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But not a gentile, as reflected in Halachah 7. When speaking of this obligation, Leviticus 5:21 uses the term “a colleague,” thus excluding one who is not of the Jewish faith.

In most instances, the robber will not be required to take an oath to clear himself from the claim of the plaintiff (for according to Scriptural law, an oath is required only when the defendant admits part of the claim, the plaintiff’s claim is supported by the testimony of one witness, or the defendant was a watchman). Instead, he is voluntarily taking this oath or voluntarily responding Amen to an oath suggested by the plaintiff. See Hilchot Sh’vuot 7:1.

See Halachah 8.

In the original Hebrew a plural form is used, for there are times when this additional amount will be increased, as explained in Halachah 13.

E. g., if the original obligation was four, he must now pay five. (See Halachah 7.)

See Leviticus 5:20-25, where these obligations are described.

This excludes a fine (קנס), i.e., a payment of more or less than the principal, for which a person is not liable on the basis of his own admission. He must be convicted on the basis of testimony of witnesses.

For if the son did not know of the matter, one would never suppose that he would be liable, for he is not considered to have taken a false oath.

The liability of a son for robbery committed by his father is discussed in Chapter 5, Halachot 5-6.

And the son is liable to return the value of the article obtained by robbery, but not the article itself.

For in this instance, the heir himself is obligated to return the object obtained by robbery. Failing to do so and attempting to avoid his obligation by taking a false oath is equivalent to taking the article from its rightful owner. Therefore, he is liable for the additional amount.
The Sefer Mitzvor Gadol states that the son need not bring a guilt offering, but this view is not accepted by all authorities.

Since the robber admitted his guilt, he became liable for the addition of the fifth before his death. His estate remains responsible for that obligation after his death.

For the robber died without admitting his guilt. As stated in Halachah 8, the additional fifth is a penalty that brings atonement for the transgressor. Since the heir did not sin, he is not required to pay this penalty to achieve atonement.

I.e., in the situations described in this and the previous halachah.

For the guilt offering is intended to bring atonement for the robber, and there is no concept of a person’s gaining atonement through sacrifices once he has died.

I.e., excluding a plaintiff who is not a fellow Jew.

See also Halachah 12.

This concept applies whenever the Torah mentions the concept of adding “one fifth.” See Hilchot Arachin 4:5.

See the Tosefta, Bava Kama 8:3, which indicates that if the defendant admits his guilt after the witnesses testify, he is obligated to bring a guilt offering and pay an additional fifth.

In the Guide for the Perplexed, Volume III, Chapter 41, the Rambam states that the sacrifice and the additional fifth atone for the sin of taking a false oath.

In his Commentary on the Mishnah (Bava Kama 9:8), the Rambam cites Leviticus 5:23 as a proof-text, which speaks of the return of an article obtained by robbery. From the context of the passage, it is obvious that the Torah is speaking of a person who returns the article in an attempt to seek atonement.

And bring the money to him, regardless of where he is located.
Sefer Me’irat Einayim 367:4 maintains that this is one of our Rabbis’ ordinances employed to encourage robbers to repent. The Siftei Cohen 367:2 differs and maintains that even according to Scriptural law, there is no need to seek out the owner.

We assume that since the robber did not take a false oath, the matter remains open, and the owner is planning to return and sue for the return of his money.
The Tur (Choshen Mishpat 367) states that while the owner is away, the robber must, however, try to notify him that he has his property and is prepared to return it. The Ramah (Choshen Mishpat 367:1) quotes the Tur’s comments. Nevertheless, from the context it appears that the Ramah’s intent is that the owner should be notified when he returns.

Bringing a sacrifice will not convey atonement upon him until the article obtained by robbery is returned. This is the reason given by Bava Kama 103a. The Siftei Cohen 367:6 questions why the Rambam ignores the rationale given by the Talmud and instead mentions a reason that he arrived at himself.

Bava Kama 103a derives this from Leviticus 5:24, which states: “He must give it to its owner.” Sefer Me’irat Einayim 367:5 states that even when the robber did not take a false oath, he is not able to return the object obtained by robbery to anyone but the owner himself.

This fulfills his obligation to return the object obtained by robbery, and he may attain atonement by means of the sacrifice.
Bava Kama 103b explains that this is one of the leniencies adopted by our Sages in order to encourage people to repent. In this manner, the expense of the journey to find and return the object obtained by robbery will be undertaken by the court and will not have to be borne by the robber.

Once the principal has been returned, the robber has met the fundamental financial obligation incumbent upon him (and he can thus attain atonement via a sacrifice). Hence, he is not required to seek out the owner to return the additional fifth.

The owner’s waiver of payment is equivalent to his receiving the money due him.

For, as mentioned above (Halachah 7), less than a p’rutah’s worth is not significant, and it is considered as if the object obtained by robbery has been returned in its entirety.

The article obtained by robbery itself must be returned to its original owner. Although the portion of the article concerning which the owner did not waive payment was originally worth less than a p’rutah, that portion is still considered to be in the possession of its owner. Thus, when the value of the article as a whole increases, the value of this portion also increases, and it is possible that it will be worth more than a p’rutah. (In which case the robber would have to seek out the owner, as stated in the following clause.) We are, however, not concerned about this possibility and consider it as if the article has been returned.
Note Sefer Me’irat Einayim 367:8, which quotes opinions that state that even if the article does increase in value to the extent that the remaining portion is worth a p’rutah, the robber is not obligated to return it. Since he was absolved of his obligation originally, he does not become liable again.

I.e., as long as the robber owes at least a p’rutah’s worth of the principal, he must seek out the owner and return it to him.

E. g., the obligation to seek out the owner and return the money due him.

I.e., a fifth of the original fifth. For example, if the object obtained by robbery was worth 16 [zuz], the original fifth was four, and the fifth of the fifth is one.

For he is required to seek additional atonement for this second misappropriation of money and false oath.

At which point an oath is not required, as stated in Halachah 7.

In this instance, the intent is that every additional fifth is one fourth of the value of the original article.