Chullin, Chapter 5, Mishnah 4. This chapter has been occupied with the prohibition of oto ve'et beno, slaughtering a mother animal and its offspring on the same day. The previous mishnah listed four occasions during the year when the pressure of business is so great that a special warning is issued: days of festivity and feasting, when a person buys an animal and wants it slaughtered on the spot. There the four days were relevant to oto ve'et beno. Here the very same four occasions are brought up again, but for an entirely different halachic issue: what a buyer can demand of a seller, and how a sale is completed.
The language of the mishnah is "be'arba'ah perakim eilu", during these four periods of the year, if a person purchases an animal from a dealer and asks to have it butchered for him right away, then "mashchitin et hatabbach", the butcher is put to work slaughtering it, "be'al korcho", whether he is willing or not.
Even a Single Dinar's Worth
How far is this taken? The mishnah pushes the case to its outer limit: "afillu shor sheshaveh", even an ox valued at "elef dinarim", a thousand dinarim, and yet "ve'ein lo lalokeach", the purchaser's stake in the animal amounts to no more than "ella dinar", one single dinar, a sliver of the whole, still "kofin oto lishchot", the butcher is compelled to carry out the shechitah. He may be left holding an enormous quantity of meat with nobody waiting to buy it, and that consideration carries no weight. Once the purchaser owns a portion of this animal, he has the right to insist that it be slaughtered, so that he can collect what belongs to him and eat it as he pleases.
Payment Alone Completes the Purchase
What is striking here is that the buyer paid for his share and did nothing more. He performed no meshichah, no act of drawing or taking hold of the animal, nothing that would ordinarily serve as an act of acquisition. Yet the Chachamim rule that on these four occasions handing over the money is sufficient, and no further act is required of him.
On the level of Torah law, payment does in fact function as a valid kinyan. It was the rabbis who legislated that money alone should not finalize a sale, and that the purchaser must perform a physical act in order to take genuine ownership. What the mishnah teaches is that on these four days that rabbinic requirement is set aside, and the underlying Torah law is allowed to operate.
Why? Because on these days the demand for animals to slaughter was enormous. Everyone needed meat for their celebrations and their festive meals. Under those conditions every purchaser wants his payment to seal the transaction on the spot, so that the seller will not turn around and back out of the deal when a better offer appears. The Chachamim therefore ruled that on these four occasions payment alone acquires the animal, and consequently the buyer may compel the butcher to slaughter it.
The Consequence: Who Bears the Loss
"Lefichach, im met", therefore, if the animal dies before it is slaughtered and becomes a neveilah, "met lalokeach", the loss falls on the buyer. Since ownership of his share had already passed to him, he absorbs the loss on his portion and cannot demand his money back from the seller. At the moment the animal died, that share was his.
The Rest of the Year
"Aval bish'ar yemot hashanah", throughout the remainder of the year, "eino chen", the rule is different. Someone who purchases an animal, or a fraction of one, on an ordinary day when there is no crush of slaughtering, has no power to make the butcher slaughter for him. Everywhere else the usual halachah governs: cash does not effect the kinyan, and the purchaser is obligated to make a real act of acquisition. As long as that act has not taken place, no portion of the animal belongs to him, and with nothing of his own at stake he has no claim with which to press the seller to slaughter.
"Lefichach, im met", therefore, in that case, if the animal dies before the shechitah and becomes a neveilah, "met lamocher", the loss belongs to the seller. He is the one who suffers, and he must refund the buyer's money, since the buyer never came to acquire anything at all.