Question: I was on a bus, and someone did not have enough money on their Rav-Kav (transit card) to pay. He asked if I could pay for him and pay me back in cash. The bus fare was 14.50 NIS, and neither of us had enough small change to work out exact payment, so he handed me a 20 NIS bill and send “It’s fine,” and he indeed did not seem to care much. I am a 12-year-old, and my parents put the money on my Rav-Kav. Can I keep the extra money he gave me, as I was the one who made the deal, or do I have to give it to my parents?

Answer: Since you ask a precocious question, I can give you a serious answer with the basic halachic analysis and sources – a full treatise would be too long.

The gemara (Ketubot 98b) discusses a case where Reuven gave Shimon money to buy something for him and the seller purposely gave Shimon more of it than the normal price indicates. The gemara says that if the price of the commodity is fluid, all that was given goes to Reuven. If the price is set, the extra received is split between Reuven and Shimon. Rashi (ad loc.) explains that if the price is fluid, we view the ostensible extra as an integral part of the sale, and the sale of course was done on Reuven’s behalf. However, if the price is set, the extra is viewed not as part of the sale but as a present. The reason the clear extra is divided between Reuven and Shimon is that we do not know who the intended recipient is.

The Rif (ad loc.) explains differently. He views Shimon as the natural recipient when the price is set, but since he was only able to make the deal due to Reuven’s money, Reuven deserves half of the extra produce. The Rama (Choshen Mishpat 183:6) prefers Rashi’s approach (which surprised the Shach, CM 183:12) and therefore says that if the seller said he intended the extra for Shimon, Shimon receives it all.

The simple application of this rules is to say that validating a fare has a set price, which is why your acquaintance looked for 14.50 NIS. This would make the extra 5.50 NIS a present, either to you as a helpful young man or to your parents, who trained you to use their money to help someone; you would thus split the 5.50 NIS. However, it is also possible your acquaintance did not intend for a present but to save the time/embarrassment of trying to get change. Under the circumstances, this would be a natural way of buying the fare or reimbursing the money (one could argue either formulation), so the whole 20 NIS would go to your parents. So, the halachic picture is murky.

According to the strict Halacha, parents who support their child are entitled to claim the objects their child finds (see Bava Metzia 12b). This halacha is true for a gift a supported, minor child receives as well (Rama, CM 270:2). Therefore, even if you deserve some of the extra money, as a present, your parents are able to take it from you. It is true that it is very common nowadays for parents to waive this right. However, you should not necessarily assume that regarding the money in question, for which there are strong indications that your parents have a claim irrespective of your relationship, your parents would waive their halachic right.

Let me give you advice about handling questions of permission needed from someone who has asymmetrical authority (e.g., parents, employers), who, due to legal, halachic, and/or practical reasons, have the right to decide. People often ask whether they may assume implicit permission for this or that. My frequent advice is – it is more respectful and you are more likely to receive the permission if you ask them. In this case, (parents, see Fifth Commandment) I suggest that instead of asking, “Can I keep the money?” announce “Here is the 20 shekels I got for use of the Rav Kav.” If your parents take it, they deserve it for all they do, and that might be the best chinuch. If they return the difference, you will have a nice feeling. If you discussed it, and your parents suggested seeking out the Halacha, that is wonderful.

Best wishes for continued personal growth, and mazal tov on your upcoming bar mitzva.