By the Bais Hora'ah
My friend is a maggid shiur in a mesivta, and was planning to travel overseas for his son’s wedding. He asked me to substitute for him for a full week, and offered to pay me not only his $1,000 weekly salary, but also the $200 difference between his salary and mine, which I would forfeit by taking off the week from work.
When I returned to work, my employer surprised me. Although he generally docks pay for even one day off of work, at the end of that week he decided to pay me $600 – half of my weekly salary.
Obviously, I am entitled to the $1,000 my friend received from the mesivta, and to the $600 my employer generously decided to give me for that week I took off. My question is whether I can also keep the $200 my friend paid me to compensate for the difference between our salaries. He has no idea that my employer paid me for half that week’s work, and he had initially agreed to pay the difference between our salaries in order for me to agree to substitute for him, so perhaps the money is mine. On the other hand, since he only agreed to pay that difference as compensation for my loss, and I didn’t lose that amount, must I return the difference to him?
A. You are allowed to keep the $200.
The Gemara (Bava Kamma 116a) discusses a case in which a river sweeps away two people’s donkeys simultaneously. Reuven’s donkey is worth twice as much as Shimon’s, and Shimon offers to save Reuven’s donkey on condition that Reuven reimburse him for his donkey, which would likely drown in the interim. After Shimon saves Reuven’s donkey, they notice that Shimon’s donkey managed to emerge from the water alive.
The Gemara deliberates what the halachah is in this case: On one hand, we might say that at the moment when Shimon agreed to abandon his own donkey in favor of saving Reuven’s, he was mafkir (released possession of) his donkey, and Reuven was immediately obligated to pay him for it. When Shimon’s donkey reemerged, he took possession of it from hefker, but that does not absolve Reuven from paying for it. On the other hand, perhaps Reuven only agreed to pay the price of Shimon’s donkey because he assumed that it would die while his donkey was being saved, but he never agreed to pay for Shimon’s donkey if it survives. Now that Shimon’s donkey survived, perhaps Reuven should have to pay Shimon only for the time expended on the rescue, but not for the donkey (Shittah Mekubetzes, citing Rabbeinu Yehonasan).
The Gemara concludes that Rav says that “in Heaven they took mercy on him (i.e., Shimon).” Since it was unlikely that Shimon’s donkey would survive, and it was spared only by Heavenly mercy, Reuven is required to pay Shimon the full value of his donkey (Shulchan Aruch Choshen Mishpat 264:3).
The poskim explain that because his donkey is worth so much, Reuven agreed to pay Shimon to save it and abandon his own donkey, which would then likely drown. Once they made this agreement, it is considered as though Reuven hired Shimon to save his donkey, with the wage set at the full value of Shimon’s donkey. The fact that Shimon’s donkey happened to survive does not reverse that agreement, because the fact that Shimon did not suffer the financial loss he had agreed to risk was due to Divine mercy on his behalf (see Nesivos 262:3 and Ohr Samei’ach, Hilchos Sechirus 7:1).
Returning to your case, when you agreed to substitute for your friend, you did so under the assumption that you were forfeiting your salary from your employer for that week, and your friend agreed to compensate you for that loss. The fact that your employer decided to pay you has no bearing on your agreement with your friend, so you are allowed to keep the extra $200.
Other poskim explain the case of the Gemara in another way: When Shimon jumped into the water to save Reuven’s donkey and not his, he completely forfeited his rights to his donkey and made it hefker. When he then retrieved it as it stepped out of the water, an act of Divine mercy enabled him to acquire it anew from hefker – which is akin to him taking possession of someone else’s lost object (Chazon Ish, Bava Kamma 18:3).
According to this explanation as well, when you agreed to substitute for your friend, it was as though you forfeited your rights to the additional $200 you would have been paid by your employer, who had no obligation to pay you for that week, and your friend agreed to compensate you for that loss. The $600 your employer then decided to pay you has no bearing on your earlier agreement with your friend (see Shu”t Igros Moshe, Choshen Mishpat 1:37).