1) IS ONE OBLIGATED TO COMPENSATE ANOTHER PERSON WHOM HE PREVENTED FROM MAKING A PROFIT?
QUESTION: Rav Chama rules that when a person is appointed to purchase a certain quantity of a commodity (such as wine) for someone else at the present market price, and he is negligent and fails to purchase it and the price goes up, he must deliver the same quantity of wine that he could have bought at the lower price, compensating for the difference from his own funds. Rav Zevid qualifies Rav Chama's ruling and states that it applies only when the buyer told the agent to purchase wine, without specifying any particular winemaker's wine. If, however, he instructed the agent to buy for him specific wine, the agent is not responsible if he fails to buy the wine, because perhaps the winemaker would not have sold it to him. Rav Ashi argues and says that even if the buyer did not specify any particular wine, the agent is not responsible if he fails to buy wine at that price, because the agent's acceptance of responsibility was an Asmachta, and the Halachah is that an Asmachta is not binding.
Rav Chama, Rav Zevid, and Rav Ashi disagree about whether or not a Shali'ach's acceptance of responsibility for a lost opportunity for profit is considered an Asmachta. They would agree, however, that if an Asmachta would be binding, the Shali'ach would be obligated to compensate for the loss.
The Rishonim point out that this conflicts with the Yerushalmi (Bava Metzia 5:3) which states that one who "ties up" another person's funds (rendering him unable to profit from them) is exempt and does not have to pay for the lost profit, because it is considered only a "Gerama," an indirect cause of loss to the owner of the money. In the case of the Gemara here, the Shali'ach's failure to buy the wine at the low price is an indirect cause of loss to the buyer. Why, then, should he be obligated to compensate for the loss (if not for the problem of Asmachta)?
(a) The RITVA offers two answers. In his first answer, he explains that the Gemara is discussing a specific case in which the Shali'ach -- upon taking the money -- agreed to pay for any loss that might result from his negligence. Since he made an explicit agreement, he is committed to honor that agreement (if not for the fact that it is an Asmachta). When the Shali'ach made no agreement, then indeed he is not obligated to compensate for the loss, as the Yerushalmi states, because it is a "Gerama," an indirect cause of loss, for which a person is exempt.
The reason why the Gemara does not mention that the Shali'ach explicitly made an agreement obligating himself to pay for any loss is that it is obvious that such an agreement was made; without such an agreement there is no reason to obligate the Shali'ach (as the Yerushalmi states).
(b) The Ritva answers further that even without a specific agreement to obligate himself, the Shali'ach would be obligated to pay for a loss caused by his negligence. The reason is that the Shali'ach is considered an Arev, a guarantor. In the case of an Arev who guarantees a loan, the Arev becomes obligated to repay the loan (if the borrower cannot) by virtue of the fact that the lender handed over money (to the borrower) only on the Arev's word that he would pay back the loan. Similarly, in the case of the Gemara here, the buyer gave the money to the Shali'ach only because of his reliance on the Shali'ach's word that he would purchase the wine for him. The Shali'ach, therefore, became an Arev for the money.
This answer has broad, practical ramifications. Any hired worker who quits his job and thereby causes a loss to his employer (by requiring the employer to pay more for a new worker) is liable to compensate for the loss based on the Halachah of Arev. This Halachah also applies in the converse case, in which the employer fires the worker, thereby causing the worker a loss. Since the worker agreed to work for this employer (and to forgo employment elsewhere) based on the employer's word that he would pay him, the employer is considered like an Arev who is responsible to pay the worker. (Y. MARCUS)