בבא מציעא ד׳:א׳ - ד׳:ב׳

הזהב קונה את הכסף – Each thing that is considered to be a coin and currently passing to be given in expenditure (of money), it has the law of coinage. But where it is not considered to be a coin and currently passing, it has the law of merchandise. And his taking possession by drawing towards one’s self the object to be acquired is the establishment of the matter. Therefore, from when one draws [towards oneself] the gold denar, the second has acquired the silver denar in whatever place they are, and neither one of them can retract in this, for the golden denars are [considered] produce in regard to the silver denars.

והכסף אינו קונה את הזהב – since the silver denars are currently passing in expenditure [of money], they have the law of money with regard to golden denars. And if one [of them] pulled the silver denars, the other did not acquire the golden denars, until he pulls [the golden denars], for the money does not purchase, and that is the reason also why cooper acquires the silver, for pennies of copper whose passing is not so important [in the expenditure of money], they are produce in regard to the silver denars, and the silver does not purchase the copper.

מעות הרעות – which became invalidated

אסימון – that was made in the manner of current coinage but it still had not stamped upon it a feature.

כל המיטלטלין קונין זה את זה – if he exchanged these for those, since the one that pulled/drew towards one’s self, the other fellow acquired [the other object]. And this word כל/”all” – includes even a purse filled with money [in exchange] for a purse filled with money.

נתן לו מעות ולא משך ממנו פירות יכול לחזור בו – [both] this one and that one. And it is an ordinance of the Sages, for according to the Written Torah, money does acquire, as we found concerning property dedicated to the Temple, as it is written (Leviticus 27:19): “[and he shall give the money] and it shall pass to him.” And what is the reason that they said that pulling/drawing towards one’s self acquires and not money? It is a decree lest the purchaser leave his acquisition in the seller’s house for long time and a fire spreads in the seller’s neighborhood and he would not be troubled to do what was required to save [what he sold]. Therefore, they placed them in his permission to retract from it (i.e., the sale) if he desired, for since if they increased in value while in his possession, it would increase [in value] and he would retract from the sale and the profit would be his. It is considered by them to be his and he would go to the trouble to save [it].

אבל אמרו מי שפרע וכו' – even though he is able to retract from [the sale]. We curse him in the Jewish court and say about him: He who punished the men of the generation of the Flood and from the generation which witnessed the separation of races (i.e., the Tower of Babel) and from the men of Sodom and Gomorrah and from the Egyptians who drowned in the sea, he will punish him who does not stand by his word (although the court cannot compel him – see Tosefta Bava Metzia 3:14; Talmud Bava Metzia 47b), and afterward he returns to him his money.

רבי שמעון אומר: כל שהכסף בידו ידו על העליונה – Rabbi Shimon is referring to the matter of the First Tanna/teacher [of our Mishnah] who said: “he gave him money, but [the other] did not draw from him towards himself the merchandise – may retract,” whether it is the seller or the purchaser, and Rabbi Shimon comes to say that sometimes the person who has the money in his hand, the seller, who received the money, has the upper hand, and it is in hand to uphold the sale if he wants, but the purchaser cannot retract in it, such as [for example], the attic of the purchaser was lent to the seller, for now if the seller wishes that the sale is upheld, the purchaser cannot retract, even though he has not pulled the object towards himself. And what is the reason why the Rabbis have stated that “pulling” acquires and not money? It is a decree lest the seller will say to the purchaser: “your wheat has burned in the attic;” here where it is the attic of the purchaser, if a fire broke out , he would trouble himself and bring it (i.e., the wheat). But the Halakha is not according to Rabbi Shimon, but rather, even though the attic of the purchaser has been lent to the seller, all the while that he has not drawn [the wheat] towards himself, he can retract, whether he is the purchaser or the seller.