Gemara

103a (Mishnah): If Reuven stole a Perutah from Shimon and swore that he did not, Reuven must return it, even if Shimon lives overseas;

It is not enough to give it to his son or Shali'ach (messenger), but it suffices to give it to a Shali'ach of Beis Din.

104a (Rav Chisda): If David made Levi a Shali'ach (to take what Moshe owes him), he is considered a Shali'ach (if Moshe gives it to Levi, Moshe is exempt, even if David never gets it).

(Rava): He is not considered a Shali'ach.

Rav Chisda says that he is a Shali'ach. David bothered to appoint him in front of witnesses, so what is given to Levi will be considered to be in David's Reshus!

Rava says that he is not a Shali'ach. David merely informs Moshe that Levi is trustworthy. If Moshe wants to rely on him, he may.

Question (against Rav Chisda - Mishnah): It is not enough to give it to his son or Shali'ach.

We must say that the Shali'ach was appointed in front of witnesses. If not, we would not know that he is a Shali'ach!

Answer (Rav Chisda): The Shali'ach was his housemate or hired help.

Question: This implies that if he was appointed in front of witnesses, he would be a valid Shali'ach. If so, why does the Reisha allow giving it to a Shali'ach of Beis Din? It should teach that sometimes he can give it to Shimon's Shali'ach, i.e. if he was appointed in front of witnesses!

Answer: The Mishnah prefers to discuss a Shali'ach of Beis Din, for this always suffices (whether Reuven or Shimon appointed him). A Shali'ach appointed in front of witnesses works only sometimes (if Shimon appointed him). Our Mishnah is unlike R. Shimon ben Elazar.

(Beraisa - R. Shimon ben Elazar): The thief is exempt after he gave it to a Shali'ach of Beis Din. I.e. the owner appointed the Shali'ach. Alternatively, the thief appointed a Shali'ach, and the owner's Shali'ach took the theft from this Shali'ach.

(R. Yochanan and R. Elazar): A Shali'ach made in front of witnesses is considered a Shali'ach.

104b (Shmuel): If Reuven had money deposited with Shimon, and he sent Levi with a letter saying to send it with Levi, and Reuven's stamp is underneath, Shimon may not send it, even if witnesses signed on it.

(R. Yochanan): If witnesses signed on it, he may send it.

Question: According to Shmuel, how can Reuven retrieve his money?

Answer: He can do like R. Aba (he can transfer ownership of the money to the Shali'ach Agav (along with) any amount of land).

Rishonim

Rif: The Halachah follows Rav Chisda, because R. Yochanan and R. Eliezer hold like him. Rabah is a minority against the majority. I.e. if the thief gave it to the Shali'ach and it was lost due to Ones, the thief is exempt. He need not give it to the Shali'ach. Any Harsha'ah (power of attorney) that does not say 'go claim and acquire for yourself' is void, for the one holding the money can say 'you have no claim against me.'

Hagahos Maimoniyos (2): R. Baruch says that the Rif rules like Rav Chisda, but also like Shmuel, who says that we do not send money based on a stamp. To avoid a contradiction, we must say that Rav Chisda's Chidush is bigger than Shmuel's. The Gemara asked 'according to Shmuel, how can Reuven retrieve his money?' I.e. he holds that one may not do like Rav Chisda. The Halachah follows Rabah; a Shali'ach with witnesses is not a Shali'ach. Rav Matisyahu Gaon and the She'altos rule like this. However, if he said 'send it with my son', he is a Shali'ach (Bava Metzia 98b).

Rambam (Hilchos Gezeilah 7:10): (If Reuven stole from Shimon and swore,) he may not give it to Shimon's son or Shali'ach, unless he was appointed in front of witnesses. If he brought the theft and Chomesh to Beis Din in his city, he may bring his Asham, and Beis Din will deal with the theft until it reaches Shimon. Similarly, he may give it to a Shali'ach of Beis Din. Whoever gives theft and similar matters to Beis Din was Yotzei.

Rosh (9:21): If Reuven stole a Perutah from Shimon and swore, he must return it. He may not give it to his son or Shali'ach. The Gemara says that the Shali'ach discussed was Shimon's housemate or hired help, or Shimon merely informs Reuven that Levi is trustworthy. However, if Shimon appointed a Shali'ach in front of witnesses, Reuven may give it to him and bring his Korban. It was enacted that one may give it to a Shali'ach of Beis Din and bring his Korban.

Hagahos Ashri: If the cost of returning it was more than the principal, he gives principal and Chomesh to Beis Din and need not return it to him, even if he swore.

Drishah (CM 367:2): He does not mean that one may give it to Beis Din only if the cost of returning it exceeds the principal. There is no source for this! The Mishnah said Stam that one may give it to a Shali'ach Beis Din! Rather, he means that if there will be a great expense to return it above the principal, Chachamim did not obligate him to do so. Rather, he gives it to Beis Din.

Tosfos (103a DH Aval): Rashi says that the enactment was to give it to a Shali'ach of Beis Din, who holds it until Shimon comes for it. If so, it should have said 'he gives it to Beis Din', not 'to a Shali'ach of Beis Din.' Also, the Gemara says that we do not distinguish whether Shimon appointed the Shali'ach Beis Din, or if Reuven appointed him (to take it to Shimon - these words are not in our Gemara). Rather, the Shali'ach Beis Din takes it to Shimon. Reuven has no responsibility (if it will be lost on the way), and may get atonement immediately. Our Mishnah does not discuss the enactment (Bava Metzia 37b) to leave the theft in Beis Din.

Drishah (ibid.): It seems that the Tur holds like Tosfos. Our Mishnah teaches Torah law: Reuven has no responsibility for loss on the way, and may get atonement immediately after giving it to a Shali'ach of Beis Din. Reuven pays the cost of delivery. However, the Tur says 'all the more so, he may give it to Beis Din.' Also, he should have taught that Reuven pays for delivery, and has no liability for loss on the way. Also, this is unlike the Rosh! Rather, the Tur holds like Rashi and the Rosh. The Torah requires bring it to Madai. The Mishnah allows giving it to a Shali'ach of Beis Din; this is an enactment. The Rambam holds that one leaves it in Beis Din and they deal with it until it gets to Shimon, i.e. they care for it like a deposit or Aveidah.

Poskim

Shulchan Aruch (CM 367:2): He must return the theft to Shimon. He may not give it to Shimon's son or Shali'ach, unless Shimon appointed the Shali'ach in front of witnesses. Similar, he was Yotzei if he gave it to a Shali'ach that Beis Din appointed in front of witnesses, and surely if he gave it to Beis Din.

Beis Yosef (DH ums v'Chen): The enactment was so that the thief need not pay a fortune to go himself to return the theft.

SMA (5 and Prishah 2): He is no less than a borrower, who is not Yotzei if he gave it to the lender's son or Shali'ach, until the lender gets it. The same applies to a thief who did not swear. The Gemara discussed a normal case. If Reuven did not swear, he need not bring it to Shimon, so he would not give to a Shali'ach.

Shach (8): One is Yotzei through giving it to Beis Din only if Beis Din will send it to Shimon when they want, but not if they will hold it until Shimon comes to get it.