הלכות מכירה

A person cannot transfer ownership over an article that has not yet come into existence. This applies with regard to a sale, with regard to a present or with regard to the disposition of an oral will.
What is implied? If a person states: "What my field will produce is sold to you," "What this tree will grow is given to you," "Give so and so the offspring that this animal bears," the recipient does not acquire anything. Similar principles apply in all analogous situations.

When a person sells the fruit of a date palm to a colleague, he may retract even after the fruits of the date palm have already come into existence. If the purchaser harvests the fruits, they are not expropriated from him. If either of them retracts, he is not required to receive the adjuration mi shepara.

When, however, a person sells produce at the market price, although the seller was not in possession of the type of produce, the seller is obligated to purchase the amount of produce he pledged, and give it to the purchaser. If he retracts, he must receive the adjuration mi shepara.

The following rules apply when a person sells produce at the market price, promising to give four se'ah for a sela. Even if the grain was in stalks, the transaction is completed, and if he retracts, the seller is liable to receive the adjuration mi shepara, provided either of the following stipulations is met:
a) the seller shows the purchaser that he possesses grain in his storehouse, or
b) the purchaser tells the seller in the market place: "I am relying on you." If the purchaser did not tell the seller: "I am relying on you," the seller does not consider this to be a firm agreement, and he is not required to receive the adjuration mi shepara if he retracts. For he says to himself: "Perhaps the purchaser also made such an agreement with another individual and he does not actually require this wheat."

An entity that is not in the possession of the seller cannot be acquired; it is like an entity that has not come into existence.
What is implied? When a seller says: "What I will inherit from my father is sold to you," "What my net will bring up from the sea is sold to you," or "When I purchase this field, it is sold to you," the purchaser does not acquire anything. Similar principles apply in all analogous situations.

When a person was on his deathbed and the heir desired to sell some of the dying person's property to spend the money for the sake of the burial, our Sages ordained that if the heir says: "What I will inherit from my father today is sold to you," the sale is binding. The rationale is that since the son is poor, if he is forced to wait until his father dies to sell the property, the corpse will remain unburied and be disgraced.
Similarly, provisions were made for a poor fisherman who has nothing to eat. If he says: "What my net brings in today from the sea is sold to you," the sale is binding. This was ordained to provide for his livelihood.

If a son sold property belonging to his father during his father's lifetime, but the son died in his father's lifetime, the son's son may expropriate the property from the purchasers. The rationale is that his father sold something that had not entered his domain. Thus, the property remained in the domain of the grandfather, and the grandson inherited the estate of his grandfather. Similar principles apply in all analogous situations.

The following rules apply when a person gave a colleague landed property as a present, and together with it gave him 100 dinarim through a kinyan agav. If the dinarim existed in his domain at the time he gave the present, when the recipient acquired the field, he also acquired the dinarim. If. however, the giver does not have a dinar, we do not obligate the giver to give the recipient 100 dinarim until the recipient brings proof that the giver possessed dinarim at the time the recipient acquired the present.
The same principles apply to other movable property that a person desires to transfer together with landed property through a kinyan agav. If the movable property is not in the domain of the seller or the giver at the time the recipient acquires the present, he does not acquire it. For a person may not transfer ownership over an article that is not in his domain.

When a person has entrusted an object to a colleague for safekeeping, he may transfer ownership over it, either through a sale or through a gift. The rationale is that an entrusted object is in the domain of its owner, and we operate under the presumption that the entrusted object continues to exists
If, however, the person to whom the article was entrusted denies receiving it, the owner may not transfer ownership of it. It is as if the article were lost; it is not in his domain.
Different rules apply with regard to a loan. Since a loan is given with the intent that it be spent, it cannot be transferred except through a ma'amad sh'loshtam, a convention that is not based on a motivating reason, as we have explained.
If the loan was supported by a promissory note, the creditor may transfer ownership of the promissory note with a written authorization and the transfer of the note, for there is an entity that can be transferred through which one can acquire the encumbrance it contains.

Just as a person may not transfer ownership of an article that has not yet come into existence, so too, he may not transfer ownership of an article to someone who has not come into existence. Even a fetus is considered to be someone who has not come into existence, and thus, when a person wishes to endow a fetus with an article, the transaction is not binding.
If, however, the fetus is the person's son, the transaction is binding. The rationale is that a person feels great closeness to his son.

When, however, a person tells his wife: "I will give my property to the children that you will bear," the children do not acquire anything. Since the woman was not pregnant at the time the present was given, the children had not yet reached a stage at which it could be said that a person feels great closeness for them.

When a person desires to transfer ownership of property to an animal, the transfer is not effective at all. If a person attempted to transfer part of his property to an animal or to a person who did not exist, and afterwards told a colleague: "Acquire a share of my property as this animal does," or "... as this fetus does," [the colleague does not acquire anything.
If he tells him: "You and this animal shall acquire my property," or "You and this fetus ... ," the person acquires half of the property.

What is implied? A person cannot transfer ownership over the fragrance of an apple, the taste of honey, the color of crystal or the like. Therefore, when a person desires to transfer ownership of the right to partake of the fruits of this date palm or to dwell in this home, the recipient does not acquire anything. For the transaction to be effective, the owner must transfer the house itself for the sake of dwelling in it, or the tree itself for the purpose of eating its fruit, as will be explained.

The laws applying to transactions involving property consecrated to the Temple, the poor, and vows are not the same as those involving ordinary people. If a person says: "All the offspring of my animal will be consecrated to the Temple treasury," "... will be forbidden to me," or "... will be given to charity," although the offspring does not become consecrated - because it does not yet exist - the person making the statement is obligated to keep his word,, as Numbers 30:3 states: "He must act according to the statements that he utters."

There are Geonim who differ with this principle and hold that the poor acquire only in a similar matter to that of an ordinary person. Therefore, they do not acquire an entity that has not come into existence. I do not accept these principles. My rationale is that a person is not commanded to transfer ownership of property. He is, however, commanded to fulfill his pledges to charity or to consecrate property, as he is commanded to fulfill other vows, as we have explained in Hilchot Arachin.