As one can 'teach' and say: He teaches himself a dispensation to grab it unjustly.

He is not lacking anything: He is not losing anything: It came to him for free, and even without exertion.

But, buying and selling, where that cannot be said: And even though this one also gave money to the seller - as we establish it later, that he took from both of them, one willingly and one against his will - and when they divide it, this one will take half of his money and that one will take half of his money; nevertheless it it a loss for him. For if he did not need it, he would not have sought it out, to buy it. And this one who is coming to divide [it] and to give half the money is unjustly causing him a loss.

I gave money: I want to give money.

But a found item, where it cannot be said: "Let me friend go and find another [like it]." This is certainly causing him a loss of money.

But let us see from whom he took: Let us ask the seller from whom he took the money. As we learned (in a baraita) in Kiddushin (73b), "A seller is deemed credible to say, 'I sold to this one, and I did not sell to that one.'" And even though it ends, "In [which case] are these words said? When his item that is being purchased is [still] in his hand. But if his item that is being purchased is not in his hand, he is not deemed credible." For he did not pay so much attention to the thing, that he would remember; since they both pursued him with the giving of its value. [Nevertheless,] we establish [the case] there to be when he took money from both of them, from one willingly, and from the other against his will. As since it is not incumbent upon him to testify, he was not so exacting to be careful after they went away from him [to remember, from] which one he was willing and [from] which one it was against his will. But when he only received money from one, he would certainly remember him.

No, it is necessary - as he took money from both of them: We follow this version: "And we do not know from which one he was willing and from which one it was against his will." And we do not follow the version: "And he did not know." As even if he did know, the seller is not deemed credible once they have gone, as it was established there (Kiddushin 74a).

Our mishnah: That they are both told to swear, so one will swear falsely.

Is not according to Ben Nannas: In Tractate Shevuot (45a), concerning a storekeeper [relying] on his ledger, these and those come to the court in order to make an oath, one of them in vain: A homeowner says to a storekeeper, "Give my son a dinar of wheat and I will have to pay"; or "Give my laborers a sela in small coins, which I am obligated [to pay them] for their wages, and I will have to give [you] a sela." And [later the storekeeper] says, "I gave it"; but [the laborer] says, "I did not receive it." So they both make a claim against the homeowner. Both of them take an oath and take [the money they are claiming] from the homeowner. Ben Nannas said, "How is it that both these and those come to take an oath in vain? Rather, they both take [the money] without an oath."

Say they lifted it together: About a lost object, each one holds, "I lifted it first and it is all mine." So when they swear about half of it, they are swearing truthfully. And also regarding buying and selling, perhaps [the seller] agreed to both of them.

In accordance with Sumakhos: In Bava Kamma (46a) concerning an ox that gores a cow and its fetus is found [dead] beside it.

The burden of proof rests upon him: With witnesses. But if not, he collects nothing. Whereas here, they divide [it] with an oath!

We follow this version: Granted, if you say [it is like] the Rabbis - there, where both of them are not grasping [it], the Rabbis say, etc.; here where both of them are grasping [it], they divide [it] with an oath. But if you say [it is like] Sumakhos - now, if there, where both of them are not grasping [it], they divide it without an oath; here, where both of them are grasping [it], is it not all the more so?

Both of them are grasping: So there is no claimant [to] remove it from his fellow here.

They divide it with an oath: Since it lacks collection, in that his fellow is grasping [it] - as this one is grasping all of it and that one is grasping all of it - the Rabbis do not establish [the law, such that] money may be extracted from its assumption of ownership with nothing, as we said there. [Hence] the Rabbis, who need a proof, would require them [to take] an oath.

Uncertain and uncertain: Like over there, as we learned, "The fetus was found next to it, and it is not known if it gave birth before it gored it, or if it gored it after it gave birth to it and the fetus did not die because of the goring, but rather on its own." And since each [side] is making an uncertain claim, an oath cannot be imposed on them.

Of Rabbah bar Rav Huna: In the chapter [entitled] HaShoel below (Bava Metzia 100a).

A financial association: A loss of money. For if this one pays unjustly, it will be a loss of money [for him]; and if we exempt him unjustly, it will come out that the [other] will be lacking the offspring of his cow.

If there, where there is a financial association, etc.: You cause a loss of money to whichever of them loses the half unjustly.