Rambam - 1 Chapter a Day

I.e., one of the four shades mentioned in Chapter 1, Halachah 2. Even if the increase is not the same shade as the original blemish, if it is one of these four, it imparts impurity.

See Chapter 1, Halachah 1, for a definition of this term.

Thus the person is not impure because of the healthy flesh.

For the head and beard are governed by special laws, as stated in Chapter 8.

I.e., only when it spreads on skin is it considered an increase.

The term the Rambam uses, om, relates to the word aim, literally, “the mother.”

This is speaking about a situation where the increase was not located immediately adjacent to the original blemish, but separated from it by one of these skin conditions. Accordingly, the increase is considered as a new blemish and not an increase of the existing one.

From another side.

The rationale is that since more than half the original blemish receded, it is considered to have disappeared entirely. Hence the new blemish is judged entirely independently. Since, in and of itself, that new blemish is not the size of a gris, the person is not required to be isolated.

Leaving a blemish larger than a gris, but not the same blemish that was observed originally.

I.e., it is considered as a new blemish and is observed for two weeks like other new blemishes.

This is speaking about an instance where the blemish was not observed by a priest and declared pure after it disappeared. Were that to have been the case, it would be considered as a new blemish.

I.e., we do not consider it as a new baheret that should be observed for two weeks, but as the initial one. And thus it is given only one more week of observation.

If he is at the end of his first week.

If he is at the end of his second week. The Rambam is clarifying that all the fluctuations in the size of the blemish during the period of isolation are not significant. The determining factor is the size of the blemish when it is inspected at the conclusion of the seven days.

And the afflicted person was declared definitively impure because of the increase.

I.e., after he was declared definitively impure. If he was not declared impure until after the white hair or the healthy skin erupted, he would be considered as impure even though the original blemish disappeared.

Which are considered signs of impurity independently.

If the person would be impure according to the laws that govern such blemishes, he is declared as such. See the Rambam’s Commentary to the Mishnah (Nega’im 4:10).

A coin of the Talmudic period, substantially larger than a gris.

Rav Yosef Corcus explains that the blemish must be in some way different from the original one. Otherwise, there would be no room for doubt.

I.e., we consider this as the original blemish. Were it to be considered a new blemish, he would require isolation for another week.
Here, the Rambam does not state whether the person is deemed definitively impure or considered impure only because of a doubt. From his Commentary to the Mishnah (Nega’im 5:1), it appears that the person’s impurity is a matter of question, parallel to that mentioned in Chapter 2, Halachah 9, and indeed, the Rambam intimates this point in Chapter 6, Halachah 5.

I.e., the stretch of afflicted flesh is considered as an extension of the original blemish and not an independent entity.

As stated in Chapter 3, Halachah 5. Since the entire width of this stretch of flesh is the width of two hairs, that condition cannot be met.

As the Kessef Mishneh explains, this ruling is significant if there is one white hair in each baheret. If the two are considered as a single blemish, the person should be deemed impure. If they are considered as separate blemishes, he is not placed in that category.

I.e., the two weeks of evaluation mentioned in Chapter 1, Halachah 10.

I.e., we do not consider it a new blemish which requires a new evaluation.

And no signs of impurity appear in the two weeks of isolation.

I.e., if signs of impurity reappear, he is not isolated again. He may, however, be deemed definitively impure, as stated in the previous halachah.

Because no signs of impurity were manifest.

The Ra’avad interprets this as referring to a situation in which the blemish was originally exactly the size of a gris. The Kessef Mishneh maintains that the Rambam would accept this interpretation.
Even though an increase in the size of a blemish after the person was declared pure causes him to be considered as impure, that applies only when the increase extends beyond the original parameters of the blemish.

Before inspection.

In his Commentary to the Mishnah (Nega’im 4:6), the Rambam explains that this is speaking about an instance where the lentil-sized portion of healthy flesh comes in addition to the blemish which is the size of a gris.

The white hair was located in the healthy flesh and not in the blemish. Now, as stated in Chapter 2, Halachah 6, white hair is not considered as a sign of impurity unless it is turned white by the blemish. Thus there is reason to argue that, in this instance, the white hair should not be considered as a sign of impurity. Nevertheless, since the healthy flesh is in the blemish, the hair is considered to have been turned white by the blemish [the Rambam's Commentary to the Mishnah (op. cit.)].

But the healthy flesh still remained.

This clause is speaking about an instance where together the healthy flesh and the blemish were exactly the size of a gris. Hence, there is reason to argue that the white hair should not be considered as a sign of impurity, because there was not a portion of afflicted flesh the size of a gris at the time it turned white. Nevertheless, since the healthy flesh was in the blemish, the blemish itself is considered to be the size of a gris and the white hair is deemed a sign of impurity (ibid.).

I.e., there was healthy flesh or two white hairs within the affliction.

For either of the above reasons or because the size of the blemish increased.

The person was released after two weeks of isolation, but manifested a sign of impurity afterwards, in which instance, he is deemed definitively impure, as stated in Halachah 7.