If someone who is not yet Shomer Shabbos (but G-d willing soon) buys a lunch for a Shomer Shabbos, may the Shomer Shabbos eat the food? (The concern being that the not yet Shomer Shabbos works on the Sabbath, so maybe some of the money that paid for that meal is benefitting from Shabbat desecration?) Thank you
It is beautiful to see how conscientious you are about all of the halachos. There is no need however to be concerned with benefitting from the money of the non Shomer Shabbos person. This is for a few reasons. First of all, even if the money would be problematic, since it isn’t clear that this money was indeed earned on Shabbos, and the money earned on Shabbos was mixed with the rest of the person’s money, it is permitted. Secondly, the prohibition not to benefit from Shabbos desecration is only in regard to the actual product that was produced via the chillul Shabbos. For example, a person who cooked on Shabbos; the food may not be eaten by him, or for others that he cooked it for. However the money that was given to the person because of the chillul Shabbos that he did, is not included in this because it is not a product of the chillul Shabbos. Therefore you do not have to be concerned about this at all.
M:B 318-5 in the name of the Magen Avrohom that when the product of Maaseh Shabbos gets mixed, that it is only an issue on Shabbos itself. However after Shabbos it is understood that the product is considered batel and not problematic. Additionally we don’t find that Maaseh Shabbos applies to the money that the melacha earned, but only to the benefit of the outcome of the melacha, as explained. See Biur Halacha 318 D:H Achas.