Siman 237

Our sages, of blessed memory, said [at the beginning of the third chapter of Kiddushin]: A poor person who is turning over a cake and another comes and takes it is called a rasha; however, what he has done is done if he does not return it of his own accord, and beit din does not compel him regarding this. He violates a prohibition of the words of tradition that the rabbis based on a verse in Yechezkel, that one should not descend into the livelihood of his fellow. There are some of our teachers who say that this law only applies to one who is seeking to buy something or to rent it, whether land or movable property, and the same applies if he comes to hire himself out to someone or to rent out his house or his field and anything similar to this, for why should he descend into that of his fellow when he can find this in another place? But if one comes to acquire ownerless property or to receive a gift from someone and another comes and precedes him, he is not called a rasha, since this is not something available to him in another place. And there are some of our teachers who do not hold of this distinction, and in every matter he is called a rasha. Our teacher, the Rema, wrote that the first opinion appears primary. According to this view, if one comes to buy land on the border of his fellow in a place where the law of bar metzra does not apply, such as one who buys from a woman and similar cases explained in siman 175, the neighbor may precede him and buy it and is not called a rasha, for this is like a find, as it is good for a person that his fields and houses be adjacent to one another. So too, if one is about to buy something cheaply, it is like a find, and another may precede him and buy it as long as the first has not yet acquired it. And some say that the rabbis did not distinguish regarding a sale [Shach], and it is forbidden to buy, and such is the primary view, for so it implies in the Yerushalmi there. Furthermore, it is explained there that when one is negotiating a purchase, it is forbidden for another to stand over this purchase as long as the first is satisfied to buy it, and they cursed whoever does so; therefore, a person must be careful in this. It implies there that this is even if there was not yet a finalization of the price between them. Our teacher, the Rema, wrote that all this only refers to when they have already finalized the price between them and they lack nothing but the kinyan; but if they still lack the finalization, where the seller wants such an amount and the buyer wants it cheaper, it is permitted for another to buy it, whether the seller is an Israelite or not. Thus far his words. This applies to incidental matters of commerce, but in a market where many buyers and many sellers are always found, when one is negotiating a purchase, it is forbidden for another to approach this purchase as long as the first is standing over it, even when the price is not yet finalized, as the Yerushalmi wrote [it appears to me]. So is the custom in many places, that when one stands in the market to buy something, another shall not encroach upon him; it is a beautiful custom according to the law, and they are worthy of blessing. In the Perisha, he wrote that in his days they ruled regarding this that it is hasagat gevul.

If the other person acted inadvertently, as he did not know that the first person was seeking to acquire this item and he acquired it, he is not considered a rasha; however, it is a measure of piety to leave it for the first person even in such a case [ibid. in the Gemara]. And some say that if one was seeking an item and another came and took it, and then a third person came and took it from the second, the third person is not called a rasha even if he acted intentionally.

Even according to the latter opinion that regarding any matter he is called a wicked person, this is only when the one who is seeking it is a poor person; but if he is a wealthy person, another is permitted to intervene, unless it is a matter that is not commonly found, for then even regarding a wealthy person he is called a wicked person, such as lands which are not as commonly found as movable objects [Ran ibid.].

Our teacher, the Rema, wrote that there is one who wrote that it is from the enactment of Rabbeinu Gershom Meor HaGolah not to infringe on boundaries regarding the renting of houses from a gentile, and the same applies in a place where they are accustomed to rent the loan. Thus far his words. And see what I wrote in siman 156.

It is forbidden for a teacher to hire himself out to a householder who already has another teacher in his home, unless the householder says, "I do not wish to retain my teacher." However, if a householder hired a certain teacher, another householder may hire that same teacher, and the first cannot say to him, "Go and hire another teacher," for he can say that this one will teach my son better than another teacher [Tosafot ibid.]. The concept of "one who turns over a cake" does not apply here, for this is not a monetary matter but a matter of a mitzvah, and the reason is not because it is an uncommon occurrence [it appears to me]. If the first householder already performed a kinyan with the teacher, certainly a retraction is not effective [Netivot HaMishpat], and it is forbidden for another to hire him, for he is as if acquired by the first. This is not a "kinyan of words," for the teacher has acquired his person to him [it appears to me].