Rambam - 3 Chapters a Day

The different days do not cause the transgressions to be regarded as distinct.

With regard to inadvertent transgression, it is the person’s awareness of the transgression that causes a forbidden act to be considered as distinct.

Even if the forbidden fat was cooked with different foods, the transgressions are not considered as distinct. As stated in Chapter 9, Halachah 9, with regard to the misappropriation of consecrated objects, the different pots cause the transgressions to be considered as distinct. See Keritot 15b which quotes Rabbi Akiva’s logic in explain-ing the differences between the two prohibitions.

I.e., just as the fact that the food was cooked and served in different pots was not significant for a stringency, it is also not significant for a leniency.

Hilchot Ma’achalot Assurot 14:8. This is one of the fundamental concepts with regard to the mitzvot and prohibitions concerning eating. Just as there is a minimum amount, a k’zayit (an olive-sized portion), which one must eat for a mitzvah to be fulfilled or for a prohibition to be violated; so, too, there is a minimum measure of time, k’dei achilat p’ras, in which that amount of food must be eaten. If one takes a longer time to eat the prohibited food, his eating is not significant, like one who eats less than the minimum amount.
Rashi (Pesachim 44a) offers a different view and maintains that this measure is defined as the time it takes to eat four eggs. Shiurei Torah mentions several different opinions from between four minutes until nine minutes for this period of time.

Meat left over from a sacrifice beyond the prescribed time in which it must be eaten. Partaking of such meat inadvertently makes a person liable to bring a sacrifice (Hilchot Pesulei HaMukdashin 18:10).

The Or Sameiach questions why the ruling here is different than the ruling with regard to forbidden relations with an animal, in which instance, different bodies do create a distinction. He explains that since it is impossible to be intimate with more than one animal at a time, each act of intimacy is considered separately. With regard to meat forbidden as notar, by contrast, since it is possible to partake of the different types of sacrificial meat at the same time, the different bodies do not cause the prohibitions to be considered as distinct.

Here, also, despite the fact that different bodies are involved, the prohibitions are not considered as distinct. Rav Yosef Corcus explains that since the person does not derive physical satisfaction from the slaughter of the animals, they should not be considered as distinct prohibitions.

Or wild beast or fowl (see Hilchot Ma’achalot Assurot 6:1).

This represents the Rambam’s interpretation of Keritot 22a. He understands the passage as emphasizing that the fact that the blood is in different cups does not cause the acts to be considered as distinct prohibitions. Rashi and others interpret that Talmudic passage differently.

If, however, he ate many olive-sized portions of the same type of prohibited food in one lapse of awareness, he is only liable for one sin-offering.

Sacrificial meat that was disqualified because the priest offering it had an improper intent with regard to the time when the sacrificial service associated with an offering would be performed or the time it would be eaten (Hilchot Pesulei HaMukdashin 13:1).

An issur mosif; see Chapter 4, Halachah 1, for a definition of this term.

An issur kollel. This term is also defined in that chapter.

See Hilchot Ma’achalot Assurot 14:18-19, where the Rambam explains similar concepts with regard to liability for lashes for partaking of this forbidden substance.

In his Commentary to the Mishnah (Keritot 3:4), the Rambam explains that this is considered as an issur mosif, because before he became impure, this person was permitted to partake of the meat of the animal, although he was forbidden to partake of its fat. When he became impure, since its meat became forbidden, an additional prohibition was added to its fat.
The above represents the final version of the Rambam’s Commentary to the Mishnah, as recorded in Rav Kapach’s translation of that text. The initial version of that text, which is preserved in the standard published text, states that the person had to be impure as a minor. Thus when he came of age, the prohibition against partaking of forbidden fat and the prohibition against partaking of consecrated food would be considered as two prohibitions that took effect at the same time.

This is considered as an issur mosif, because before the sacrificial fat became no tar, it was permitted to be burned on the altar. After it became notar, that became forbidden. As a consequence, that prohibition also applies to partaking of the fat.

This is considered an issur kollel, because it encompasses not only this forbidden fat, but all other foods.

For one is not liable for eating on Yom Kippur unless one partakes of this amount (Hilchot Sh’vitat Asor 2:1).

Provided the forbidden fat is worth a perutah.
This is also considered as an issur mosif, because before the animal was consecrated, it was forbidden to partake of its fat, but it was permitted to benefit from it. After it was consecrated, that became forbidden. Hence an additional prohibition also applies to partaking of it (the Rambam’s Commentary to the Mishnah, foe. cit.).

One for the violation of the Yom Kippur prohibitions and one for the violation of the Sabbath prohibitions.

The observance of both holy days commences at the same time. Although the Rambam had already stated this law in Chapter 4, Halachah 1, he repeats it to distinguish between it and the law in the previous halachah (Kessef Mishneh).

For he has not eaten enough of either prohibited substance to be liable for lashes and substances forbidden because of two different prohibitions are not combined, as the Rambam proceeds to state.

Hilchot Ma’achalot Assurot 4:17; 14:5.

One is not liable for lashes or for a sin-offering unless he partakes of an olive-sized portion of a forbidden substance. The question the Rambam deals with in this halachah is whether two half-portions of a forbidden substance can be combined to make one liable.

I.e., with regard to a person who partook of the full measure for which he is liable, there is no question that becoming aware of the prohibition makes a distinction, as stated in Halachah 1. With regard to half the required measure, there is reason to say that, since the person is not liable, the fact that he becomes aware is not significant. Hence, the Rambam emphasizes that this is not so.

Writing is one of the labors forbidden on the Sabbath. To be liable, one must write two letters (Hilchot Shabbat 11:9).

The Rambam adds the phrase, “next to the first,” for to be liable, the two letters must be read as a single unit (ibid.:11).

Here, also, the person’s gaining awareness causes a distinction to be made between the prohibited actions.

Although in the first of these instances, the transgressor is liable and above, he is exempt, in this context as well, his gaining awareness is significant, as evident from the second instance. Therefore the Rambam introduces the clause with the phrase “in a like vein.”

One is liable for transferring an article four cubits in the public domain. In this instance, the person did transfer the article that distance. Nevertheless, since he gained awareness in the interim, the question is whether the two are combined (ibid. 12:8).

Thus all that is significant is his initial intent. The fact that in the interim, he changed his intent is not of consequence (see Shabbat 102a).

Carrying it, in which instance, he could bring it back.

It is considered as if he performed three separate actions, each distinct from the other.

Were he to have set aside an animal as a sacrifice, one could understand why it would not atone for a transgression that the person did not have in mind at the time he set it aside. The Rambam’s point is that even if he did not set the animal aside, the two transgressions cannot be atoned for together.

And the one offering atones for both transgressions.

Even though with regard to intimacy, the same person is involved in both transgressions, if one becomes aware of the transgressions at different times, he is liable for two sin-offerings. Alternatively, even though one cannot engage in two acts of intimacy at the same time, one is liable for one sin-offering if he found out about both at the same time (Kessef Mishneh).

Rav Yosef Corcus emphasizes that we are speaking about a situation where the person partook of the entire amount within the time it takes to eat three eggs (k’dei achilat p’ras). Otherwise, his partaking of the food at the different times would be considered as distinct actions.

That offering atones for the olive-sized portion that he became aware of. It does not affect the second smaller portion, because a sacrifice is not required for eating less than an olive-sized portion (Rav Yosef Corcus).

He receives atonement for the first half portion when offering the sacrifice for the portion of which he became aware. Hence, it is not combined with the second half-portion.

Even though he was not aware of the second transgression at the time he offered the sacrifice, it secures atonement for him. Even though, as stated in Halachah 9, the fact that he became aware of the transgressions at different times creates a distinction between them that principle applies only when he became aware of the transgressions before the sacrifice was offered. If he does not become aware until atonement is offered, by contrast, it secures atonement for him (Kessef Mishneh). See also Chapter 7, Halachah 10, where similar laws are discussed.

From Shabbat 71a-b, one could come to the conclusion that atonement is also secured for the third transgression. Nevertheless, that approach follows the opinion that becoming aware of the transgression does not create a distinction between the transgressions. The Rambam follows the opinion that a distinction is created and, hence, requires a sacrifice in this instance. See also the notes to Chapter 7, Halachah 10.

This applies provided he becomes aware of the second transgression at the same time he becomes aware of the third or he becomes aware of it after the sacrifice was already offered (Kessef Mishneh).

Provided he did not become aware of the first or third transgressions before offering the sacrifice.

I.e., he did not know which pieces of fat he ate, the permitted one or the forbidden ones.

As explained in Chapter 8, when a person is uncertain whether or not he transgressed, he must bring a tentative guilt-offering. As explained in Halachah 8 of that chapter, in a situation where he becomes aware of the possibility that he transgressed twice at two different times, he must bring two guilt-offerings.

For one is not obligated to bring a sin-offering until he has definite knowledge of a transgression. Note, however, an exception to this principle in Chapter II, Halachah 7.

Of wine or of blood.

Of meat, fat, or incense.

As mentioned in Hilchot Avodat Kochavim 3:3, one is liable for performing these four services to any false deity, even if this is not the way it is ordinarily served.

These are the ways in which these false deities are served (see ibid.:2).

For this is considered as two lapses of awareness. The distinction between different services performed to a false deity are governed by similar laws as the distinction between different labors performed on the Sabbath. Even though one performed them in the same lapse of awareness, they are considered as separate acts (Sanhedrin 62a, Keritot 3a).

Keritot 3a states that one could come to this conclusion, because Exodus 20:20 states: “Do not make with Me gods of silver and gods of gold.”

For there is only one lapse of awareness.

Had he converted while an adult, he would certainly have learned about the Sabbath before conversion. A child who converted under the guidance of the court, by contrast, need not to have been so informed (Kessef Mishneh).

This is the definition of the term tinok shenishba. Since the child grew up among gentiles, we assume that he never was educated about the Sabbath laws. In this instance, our translation for shegagah, "lapse of awareness," is not entirely appropriate. Unlike the former instance, this person did not know about the Sabbath prohibitions and forget; he was never aware of them. Nevertheless, he is required to bring a sacrifice in atonement.

Since he is unaware of the very essence of the Sabbath prohibitions, the different forbidden labors and different Sabbaths are not of consequence.

Our translation follows the version in authoritative manuscripts and early printings. The standard published text follows a different version.

Even if he inadvertently violates several Sabbaths in succession without gaining awareness in the interim, the passage of time between the Sabbaths creates a distinction between them.

This lack of knowledge is sufficient to cause his violation to be considered as “inadvertent.” (See Chapter 2, Halachah 2).

As explained in Hilchot Shabbat, ch. 7, and exemplified with regard to every category of forbidden labor in the chapters that follow: there is a primary category of forbidden labor, i.e., activities of the same type and which share the same purpose as those performed in the construction of the Sanctuary. Thus plowing, digging, and making a groove in the ground are all considered in the same category. Nevertheless, all are considered as primary forbidden labors and not derivatives because they all involve digging in the ground and share a single purpose.
A derivative, by contrast, is an activity that produces a result similar to that produced by a primary forbidden labor, but which differs both in intent and in the nature of the activity [the Rambam's Commentary to the Mishnah (Shabbat 7:2).] In Hilchot Shabbat 7:5, he gives an example: cutting a vegetable into small pieces is a derivative of grinding. Similarly, taking a strip of metal and pulverizing it into powder is considered as a derivative of grinding.

In this instance, his lapse of awareness concerns the labors. Hence he must bring a sin-offering for every category of labor. Moreover, even if he performs this forbidden category of labor on several Sabbaths in succession, the different Sabbaths do not create a distinction. Until he learns what constitutes a forbidden labor, it is all one lapse of awareness (Rav Yosef Corcus).

The Rambam’s actual wording “40 minus 1” is a quote from Shabbat 73a.
The Kessef Mishneh and Rav Yosef Corcus (quoting a responsum of R. Avraham, the Rambam’s son) maintain that this final clause is referring to an instance where he does not know that he is liable for karet for performing the forbidden labors, for if he does not know that all the 39 labors are forbidden, how can it be said that he knows of the Sabbath?!
Alternatively, it could be interpreted as referring to a situation where the person knew that there were certain activities forbidden on the Sabbath, but was not aware of the delineation of the categories of forbidden labor. Since he did not know that all these categories of labor were forbidden, he is obligated to bring a sin-offering for each category.

Although he also had a lapse of awareness with regard to the forbidden labors, since he was not aware that the day was the Sabbath, the latter lapse of awareness is of primary importance (Rav Yosef Corcus, quoting Shabbat 70b).
The commentaries question this ruling, because the question is left unresolved by the Talmud. The commentaries explain that even though, generally, when there is an unresolved question in the Talmud, we rule stringently, in this instance, the person cannot be obligated to bring a sin-offering unless he knows with certainty that he is obligated to bring it. For, otherwise, there is the possibility that he is slaughtering an ordinary animal in the Temple Courtyard and that is a serious transgression.

Since they are in the same category of labor, atonement is secured by the same sin-offering.

I.e., one might think that when one performs the primary labor, the importance of the derivative is dwarfed, and hence, one is not liable for a separate offering. When one does not perform the primary labor, by contrast, there is room to think that each derivative should be considered individually (Rav Yosef Corcus).

The expression “It appears to me” implies a conclusion made by the Rambam on the basis of a deduction for which there exists no prior Rabbinic source. Hence, the use of that phrase here attracted the notice of the commentaries who note that this concept is explicitly stated in Shabbat 96b and Bava Kama 2a. Rav Avraham, the Rambam’s son, offers a rationale which the Kessel Mishneh easily refutes and then says that it is possible that the Talmudic passage slipped his father’s mind while he was composing the Mishneh Torah. Alternatively, Rav Yosef Corcus states that there are some activities that are considered as derivatives of two different forbidden labors. For example, removing dregs from wine could be considered a derivative of borer (separating) or mirakeid (“sifting”). If one person sifted flour and removed dregs from wine, there is a question whether he is liable for one sin-offering or two. Rav Yosef Corcus states that the ruling depends on the warning he was given. If he was warned for sifting, he is liable for one sin-offering, If he was warned for separating, he is liable for two. Rav Yosef Corcus admits, however, that this is a difficult interpretation.

This term is used to refer to activities that so closely resemble the activities that constitute the primary categories of labor that they are considered as primary labors and not as derivatives.

By replanting the head of one of the branches of the vine in the ground where it takes root, one provides the vine with an added source of nurture. This was a commonly practiced agricultural technique in the Talmudic era.

All these are considered as primary labors in the category of planting.

Hilchot Shabbat, chs. 7-12.

As described in the second paragraph of this halachah.

As described in the following halachah.

In his Commentary to the Mishnah (Keritot 3:10), the Rambam compares this to a situation where a man is intimate with several women who are all forbidden to him because of the same prohibition, e.g., two married women. There is no question that he is liable for a sin-offering for every woman.
The Kessef Mishneh questions the Rambam’s statements, because he infers that if the person performed the same forbidden activity on three successive Sabbaths, e.g., he sowed, without knowing that sowing was forbidden, according to the Rambam, he would be liable for only one sin-offering. He objects to this decision and maintains that even in such a situation, each Sabbath is considered as a distinct entity and the person should be liable for three sin-offerings.
The Kessef Mishneh ‘s interpretation of the Rambam’s intent is reflected by the changes in the Rambam’s Commentary to the Mishnah (Keritot 3:9). Initially, the Rambam spoke about a person kindling a fire on successive Sabbaths. (This version is preserved in the standard published text of his Commentary.) Afterwards, he amended the text to read as stated here. (See Rav Kapach’s translation.).
Rav Yosef Corcus maintains that the Rambam would also rule that one who performs the same forbidden activity on several Sabbaths is liable for a sin-offering for every Sabbath. He speaks of sowing, extending, and planting, only because his source, Keritot, op. cit., uses the wording melachot... me’ayn melachah achat, “activities comprising a single category of forbidden labor,” and he is being true to his source.

Even though all of these activities are in the same category of forbidden labor.

The minimum measure for which he is liable (Hilchot Shabbat 8:3, 15).

As stated in the latter clause of Halachah 2.

And did not become aware of the harvesting and grinding performed while aware that it is Sabbath, but not aware that these labors are forbidden.

The intent is that, since at this time, he is unaware of the harvesting and grinding performed while aware that it was the Sabbath, and he is bringing a sin-offering to atone for performing these labors, the sacrifice has a more inclusive effect and atones for the other forbidden labors as well. Were he to have become aware of the later transgressions before he set aside the sin-offering for the first, they would not be included in it.

The Kessef Mishneh questions the Rambam’s ruling, noting that Shabbat 71a states that, according to this logic, atonement would be granted for all the transgressions in the following situation. A person partook of two olive-sized portions of forbidden fat and then became aware of eating one of them. He then partook of another olive-sized portion while he was unaware of the second transgression and then brought a sin-offering to atone for the first transgression. In Chapter 6, Halachah 11, the Rambam rules that, in such a situation, atonement is granted for only the first two transgressions.
Among the resolutions he cites is one offered by Rav Yosef Corcus who explains that the passage in Shabbat follows the opinion that becoming aware of the transgression does not create a distinction between the transgressions. The Rambam follows the opinion that a distinction is created and, hence, requires a sacrifice in this instance.

The harvesting and grinding performed without being aware that it is Sabbath, but knowing that these labors are forbidden.

I.e., since he was not aware of performing the forbidden labors before he brought the sacrifice, the atonement for harvesting includes the harvesting performed when he is not aware that it is the Sabbath. And since grinding was performed together with that harvesting, atonement is granted for the grinding as well. A further extension to include the second grinding is, however, not possible (Shabbat 71a).

To make him liable for a sin offering. Thus if when combined, the measure he harvested is the size of a dried fig, he is liable.
The Ra’avad differs and maintains that the concept of considering the two labors as being performed together applies only with regard to granting atonement and not with regard to establishing liability. The Kessef Mishneh explains that, according to the Rambam, it is considered as if the two activities were performed in the same lapse of awareness. Hence, they should be combined in all instances.

Which does not constitute a forbidden labor.

And thus unintentionally. performed the forbidden labor of harvesting on the Sabbath. See Hilchot Shabbat 1:8.

Chapter 2, Halachah 7; Hilchot Shabbat 1:9.

Although his intent was not to ignite the coals, since they were ignited through his activity, he is liable. He is considered to be acting willfully, because he knows that stirring the coals will ignite them. There is a slight error in the standard published text of the Mishneh Torah.

In Hilchot Shabbat 1:7, the Rambam gives another example of this principle: a person who extinguishes a lamp, because he desires the oil. In both instances, the person is intentionally performing an activity that constitutes a forbidden labor. Even though he does not desire the usual object of that activity, since he consciously desired to perform that activity, he is liable.
As mentioned in the notes to Hilchot Shabbat, the Rambam’s opinion is not accepted by all authorities. Tosafot, Zevachim 92a, differs and exempts a person in such an instance and this view is accepted by the Shulchan Aruch (Orach Chayim 278:1; 334:12). It must be emphasized that even according to the more lenient view, there is a Rabbinic prohibition against performing such activities.

This term is used because of the contrast to the adjustable guilt-offering mentioned in Chapter 10.

Those mentioned in Chapter 1. In contrast, one is not liable for a provisional guilt-offering if he is unsure whether he violated those transgressions for which a definitive guilt-offering is brought, as stated in Chapter 11, Halachah 5.

Sefer HaMitzvot (positive commandment 70) and Sefer HaChinuch (mitzvah 128) include this commandment in the reckoning of the 613 mitzvot.

I.e., it shields him from Divine retribution, but does not bring complete atonement (Rav Yosef Corcus).

The measure for which one is liable to bring a sin-offering.

I.e., he definitely partook of a forbidden substance. His doubt is whether or not he partook of a measure sufficient to require a sacrifice.

I.e., he was certain that a forbidden substance was present; he was unsure whether or not he partook of it.

Who is in a state of ritual purity. See Halachah 5.

With whom he is forbidden to be intimate.

Rav Yosef Corcus questions the Rambam’s ruling, for although it is always forbidden to perform a forbidden labor on the Sabbath, it is difficult to say that the prohibition is established, because on a weekday, there is no prohibition. He explains that the intent is that the person performed a forbidden labor in the twilight hours (bein hashamashot) of Saturday night. In this instance, we are unsure whether that time is considered as part of the Sabbath or part of the weekday.

This is the version found in the authoritative manuscripts and early printings of the Mishneh Torah. The standard published text (and the version possessed by the Kessef Mishneh) reads “He performed a forbidden labor on the Sabbath, but did not know which category of forbidden labor he performed.”
According to the version in our translation, there is a definite prohibition, because the prohibition against forbidden labor on the Sabbath is constant and the person is unaware whether he committed a prohibition. According to the standard published text, he is certain he performed a forbidden labor, but since he does not know which forbidden labor he performed, he is not able to bring a sin-offering in atonement and hence, should mitigate his guilt with this offering. Based on Halachah 5, the commentaries question the version of the standard text. Seemingly, if the person knows that he performed a transgression, he is not able to bring a provisional guilt-offering.

In Hilchot Ma’achalot Assurot 1:13, the Rambam defines this term as “A hybrid that comes from the mating of a kosher domesticated animal and a kosher wild beast.” In his gloss to Hilchot Bikkurim 9:5, Rav Yosef Caro explains that the Rambam understands the term ko’i as referring to an independent species that we do not know whether to classify as a domesticated animal or as a wild beast. He maintains that the proper version of Hilchot Ma’achalat Assurot is “any animal whose classification as a domesticated animal or as a beast is doubtful is a ko’i” and he maintains that Hilchat Shechitah 14:4 serves as proof of this interpretation.

It is not known whether such an animal is classified as a beast, whose fat is permitted, or a domesticated animal, whose fat is forbidden.

With regard to a man who is intimate with a woman who is unsure whether she is married or not, see the following halachah.

As stated in Hilchot Issurei Bi’ah 4:14, according to the Rambam [i.e., this stringency is not required by the Shulchan Aruch (Yoreh De’ah 186:1)], a woman should carry out an internal examination before and after intimacy to make sure that she did not menstruate during intimacy. If she carried out such an examination and discovered blood, but did so after waiting more than the time it takes to stretch her hand under the pillow to take an examination cloth (see Chapter 5, Halachah 6), we are unsure whether a transgression was involved or not. For it is possible that she did not begin to menstruate until after relations were completed.

His brother’s childless widow whom he is obligated to marry, as stated in Deuteronomy, ch. 25; Hilchot Yibbum VeChalitzah, ch. 1.

A woman is required to wait this amount of time to remarry after she is divorced or widowed in order that no question will arise regarding the parenthood of her offspring. For we assume that within three months, it will be apparent whether the woman has conceived or not.

Since the woman was forbidden to him as his brother’s wife, the prohibition against intimacy with her is considered to have been established. Hence until it is definitely clear that she is not pregnant, the brother who is alive is forbidden to engage in relations with her. On the other hand, since it is not definitively known that the offspring is his brother’s, he cannot be required to bring a sin-offering.

If the woman conceived the child with her first husband before his passing, the prohibition against the man marrying his brother’s wife remains in effect and every time, he is intimate with her, the couple transgress. If she conceived with her second husband, their relationship is permitted.
The Kessef Mishneh notes that Yevamot 35b appears to state that a provisional guilt-offering is required in such an instance, but explains that, according to the Ram barn, that passage does not reflect the halachah. See the Rambam’s Commentary to the Mishnah (Yevamot 4:2).

The simple explanation is that once the first witness testifies, it is considered as if the prohibition has been established. Hence the second witness’s testimony cannot override that. It can, however, be explained that this principle is accepted as a given. Here we are speaking about a situation where both witnesses testify at the same time. Nevertheless, since one witness testifies that the fat is forbidden, it is considered as if the prohibition has been established (Tosafot, Keritot 11 b).

Who is not acceptable as a witness.

Although neither are acceptable witnesses, the testimony of the first is considered powerful enough to establish the identity of the object. For a woman's testimony is significant with regard to matters involving the Torah's prohibitions (Sifra, Parshas Vayikra).

If, however, the person contradicts or supports the statement of the witness and maintains that the fat was permitted or forbidden, he is not liable for a provisional guilt-offering.

The Ra’avad differs with the Rambam concerning this issue, maintaining that since there were conflicting testimonies at the outset, the existence of the prohibited substance is not considered to have been established. He offers one possible solution: the first witness told the person that he partook of forbidden fat together with permitted fat and the second witness stated that he partook only of permitted fat. The Kessef Mishneh states that it is possible that the Rambam also had that intent, but it is more likely that the Rambam maintains that the same law applies even if the lack of agreement between the witnesses’ testimony concerns only one piece of fat. Rav Yosef Caro debates both possibilities.

Thus it had been established that she was forbidden to other men.

In which instance the prohibition against relations no longer applies.

Since it was originally established that the woman was married, we continue operating under this proposition. Although the testimony of one witness is sufficient to enable a woman to remarry, that is when there are no other witnesses who contradict him. Similarly, in Hilchot Gerushin 12:19, the Rambam writes that in such a situation, a woman cannot remain married to her second husband.

It had been established that the woman had been married and thus forbidden to others. The question is whether that prohibition was lifted because of divorce. See Hilchot Gerushin 12:6.

For it was never definitively established that she had been married and thus, we do not operate under the premise that relations with her are adulterous.

One might think that the Jew would be exempt, because there was only one piece of fat before him. Nevertheless, since originally, there were two and one was known to be forbidden, it is considered as if the existence of the forbidden entity was established.

In which instance, were he to have eaten the forbidden fat, he would not be able to atone by bringing a sacrifice.

Here also, the point is that at the time that the inadvertent violation was committed, there was only one piece of fat in front of the person. Also, we are certain that he partook of the forbidden fat. Nevertheless, since we are unsure of which he ate inadvertently and which intentionally, he is liable for a provisional guilt-offering and not a sin-offering.

For he definitely partook of forbidden fat inadvertently. The fact that he did not know which piece was forbidden is not significant. See Halachah 9.

For it had been established that a piece of forbidden fat was present and both are unsure whether or not they partook of it.

Sacrificial meat left over after the time that it is permitted to partake of it, in which instance, partaking of it constitutes a prohibition. Note the distinction between this halachah and Chapter 9, Halachah 13.

We are uncertain whether twilight is considered as part of the previous day or the following day.

Chapter 2, Halachah 3.

Although this principle was stated in Halachah 1, the Rambam restates it as an introduction to the statements that follow.

Sacrificial food that was offered with an improper intent concerning time.

See Chapter 6, Halachah 4.

See Chapter 4, Halachah 2.

For each of those deeds requires such an offering.

I.e., if one partook of two olive-sized portions of fat in one lapse of awareness, but became aware of the first transgression before he became aware of the second, he is required to bring two sin-offerings, as stated in Chapter 6, Halachah 9.

For he has certainly eaten the piece of forbidden fat.

See Halachah 4.

Because he is unsure of whether or not he committed that transgression. Even though he is also unsure whether he misappropriated a consecrated article, he does not bring a sacrifice on that account, as explained in Chapter 9, Halachah 11.

For his becoming aware of the transgression creates a distinction with regard to partaking of forbidden fat. Thus he is obligated for two sin-offerings for that transgression and one sin-offering for partaking of notar. The prohibition against notar falls upon forbidden fat, as stated in Chapter 6, Halachah 2.

For he partook of consecrated food.

As stated in the first clause.

For the same logic obligates the second person as well.