Gemara

(Mishnah - R. Yosi): (If Reuven accepted deposits from two people, and forgot who gave which amount; and each claims the larger amount.) We must force the liar to lose (to induce him to admit). Therefore, neither side gets any of the money until Eliyahu comes (and resolves it, or one side admits).

37a (Mishnah): If Reuven told two people 'I stole from one of you, and I don't know from which', or 'one of your fathers deposited money with me, but I don't know which', he pays both, because he admitted by himself.

If one person deposited 100 Zuz with Reuven, and another person deposited 200, and each claims that he gave 200, and Reuven does not know who gave which, he gives each 100. We leave the rest until Eliyahu comes;

R. Yosi says, if so, the swindler does not lose! Rather, all the money is left until Eliyahu comes.

Inference: The Reisha teaches that when in doubt, we make someone pay. We do not say 'to take money from another, one must bring proof';

Contradiction: In the Seifa, Reuven does not pay due to his doubt!

Answer: If one stole, Chachamim fined him to pay out of doubt. They did not fine one who accepted deposits.

Contradiction: Sometimes one who takes deposits is fined. When one of the fathers deposited money, Reuven pays both!

Answer (Rava): Reuven is liable for forgetting who deposited when it is as if two deposited money, each wrapped by itself. Reuven is exempt when two people deposited in front of each other, for this shows that they trust each other. He need not ensure that he remembers who gave which. It is like two people who deposited one bundle of money wrapped together.

Contradiction: In our Mishnah, a thief is fined. In another Mishnah, he leaves in front of them what he stole, and walks away!

Answer: In that Mishnah, they claim from him. Letter of the law, he leaves in front of them what he stole and walks away. In our Mishnah, Reuven wants to fulfill his obligation b'Yedei Shamayim, so he pays each.

37b Question (Ravina): Did Rava really say that when two depositors gave money in two bags, the Shomer must remember who gave which?

Contradiction (Rava - some say, Rav Papa]): All agree that two people who deposited (different numbers of) animals with a shepherd, the shepherd leaves the animals in front of them.

Answer (Rav Ashi): That is when they deposited the animals in his herd without his knowledge.

Rishonim

Rif: The Shomer must pay in the Reisha, for he was negligent for not writing how much each gave. In the Seifa, they deposited together in one bundle.

Rambam (Hilchos She'elah 5:4): If two deposited together 300 in one bundle, and each claims that he gave 200, Reuven gives to each 100. We leave 100 with Reuven forever, or until one of them admits. Reuven can say 'I saw that you are not suspicious of each other and deposited in one bundle, so I did not toil to know and always remember who gave 100 and who gave 200.

Question (Lechem Mishneh and Gra CM 300:3): Why do the Magid Mishneh (Hilchos Mechirah 20:2) and Shulchan Aruch (222:2, brought below) say (regarding a purchase) that we leave the rest in Beis Din?

Rosh (3:8): The Gemara said that another Mishnah teaches that letter of the law, a thief may leave in front of them what he stole and walk away. In our Mishnah, he wants to be Yotzei b'Yedei Shamayim. This also answers the contradiction about deposits! The Gemara did not say 'Ela' (a retraction). This shows that we still must distinguish between depositing together and separately. Also, later the Gemara asks from a teaching of Rava in which depositors gave separately, and the Shomer need not remember who gave which. This shows that we still hold that when they deposited together, the Shomer is exempt even b'Yedei Shamayim, and if they deposited separately, the Shomer is liable if they claim from him. (If they do not claim, he is exempt.) When Ploni claims from David, and David is unsure, he must pay to be Yotzei Yedei Shamayim. Here is different, for each is sure.

Note: Piplulei Charifta (400) explains that the Shomer is sure that he received a total of 300. The Bach (6) says that the text should say 'each is unsure'.

Rosh (ibid): When they deposited separately, Reuven is liable when both claim Vadai from him. They swear and collect like they claim. If they do not claim, he is liable b'Yedei Shamayim. If they deposited in front of each other, Reuven is exempt (b'Yedei Adam) when both claim from him. If they do not claim, he is exempt even b'Yedei Shamayim.

Poskim

Shulchan Aruch (300:1): If two deposited together 300 in one bundle, and each claims that he gave 200, Reuven gives to each 100.

SMA (5): The text of the Rif and Rambam says that they gave in one bundle. They hold that if they did not give in one bundle, even if they deposited in front of the other, it is as if they deposited at different times, and he should have been careful. The text of Rashi, Tosfos, the Rosh and Tur is 'if they deposited in front of each other, he owes only 100 to each. He can say 'I was not careful, for I saw that you do not suspect each other.'

Shach (7,8): This is even if they claimed, and all the more so if they did not claim. Alternatively, if they do not claim at all, the last 100 is split among them. We do not divide the money when there is a Vadai liar.

Shulchan Aruch (ibid): We leave 100 with Reuven (Rema - some say that it is left in Beis Din) forever, or until one of them admits to the other.

Darchei Moshe (2): The Mordechai (274) says that we do not leave the rest with Reuven, lest Reuven scheme to say that he does not remember, in order that the rest will remain with him.

Shach (10): Many say that we leave the rest with Reuven. The Mordechai cited the Rambam so say that it is left with Beis Din, but the Rambam does not say so! The Mordechai says that Reuven will scheme to say that he does not remember. The depositors caused their own loss by depositing together! They are scheming, for each claims 200! Since one of them schemes, we are not concerned lest Reuven schemes. In any case it seems that Reuven must swear Heses that he is unsure. He must swear even if he wants to leave the rest in Beis Din.

SMA (8): If they agree to split the rest, we give it to them, like the Shulchan Aruch (Sa'if 4) says about animals.

Shulchan Aruch (ibid): Reuven can say 'I saw that you are not suspicious of each other and deposited in one bundle, so I did not toil to know and always remember who gave 100 and who gave 200. He is exempt even b'Yedei Shamayim.

Shach (11,12): This is like the Nimukei Yosef, Semag, Tosfos, Ramban and Rashba. The Tur and Rosh disagree. The Shulchan Aruch in Siman 222 (brought below) is difficult.

Rema: Some say that if they claimed from him, to be Yotzei Yedei Shamayim he is liable even in such a case.

Shulchan Aruch (CM 222:2): If one does not know from which of five he bought and each claims from him, he hands over the money between them and leaves. Beis Din holds it until they admit or until Eliyahu comes. A Chasid pays each to be Yotzei Yedei Shomayim.

Question (Shach 6): Regarding a (blameless) Shomer, the Shulchan Aruch does not require paying each to be Yotzei Yedei Shomayim! Perhaps the Shulchan Aruch distinguishes a buyer from a Shomer. However, it explains that the buyer is blameless!

Answer (Ketzos ha'Choshen 5): Often the Shulchan Aruch teaches liability b'Yedei Shomayim. He teaches that a Chasid must pay each to be Yotzei Yedei Shomayim; others need not.

Rema (Sof 49:7): If two people in a city have identical names, and Ploni admits that he owes to one of them, but neither has a document, they can force him to pay only through a Harsha'ah (power of attorney).

Tumim (16): The same applies to two who deposited together, and afterwards each claims that he deposited 200. The Ritva holds that the Shomer holds the money until Eliyahu. According to the opinion in the Rema that the money is left in Beis Din, also here Ploni should give it to Beis Din! Why didn't the Rema say so here?

Gilyon Maharsha (CM 138:1 DH Zeh Omer): When two are holding a Talis and each says 'I wove it', Rashi says that since there is a Vadai liar, we leave it. The Tur says that the Ramban agrees. However, Shitah Mekubetzes (DH v'Zeh) cites the Ramban to say Kol d'Alim Gevar (whoever overpowers will take it) is Beis Din's withdrawal from the case. It is just like leaving it (but 'we leave it' only when a Shomer already holds it).