I tried to understand what Rav Shach and Reb Aaron Kotler are saying about the subject in Bava Metzia page 48. I cannot say I understand either. However, on the way back from the sea, it occurred to me what I think Rav Shach is saying. The Rambam wrote that when a Jew buys from a gentile (without picking up the object), and pays with money of hekdesh, the Jew transgress meila, using money of the temple for secular benefit. But when the Jew buys from another Jew, and pays with money of hekdesh (without picking up the object), he does not transgress meila. Rav Shach asks on this, and I think he is asking that even when the Jew buys from another Jew, he should transgress the prohibition because from the law of the Torah money acquires. Now this is what I think about this. The decision of the Rambam is no problem because it is directly from the gemara in Avoda Zara page 63. If one pays with a sheep to a prostitute that is a gentile, she acquire it even before she picks it up because money acquires, and the sex is in place of the money that pays for the sheep. This can also be considered to come directly from the Gemara in Bava Metzia page 48 because the braita that Rava brings as support to Reish Lakish can easily be thought to refer to a gentile as Tosphot writes there. The only question is what is the reasoning behind all this. According to the Baal Hameor the law that a Jew acquires by means of pulling is for the benefit of the seller. The Ramban disagrees and hold it is for the benefit of both. But in either case it is for the benefit of the parties involved. Therefore, in the case where a Jew buys an object from a gentile, there is no decree off the sages for the benefit of the gentile. Therefore, he acquires the money that is paid to him immediately even if the Jew does not acquire the object until he picks it up (as the Maharam from Lublin writes in Avoda Zara page 63. Therefore, the Jew transgress meila immediately because the money has gone out of the domain of hekdesh. And even though Rav Shach brins from achronim that the Rambam does not hold with change of domain, still there is plenty of evidence that he does. For example, he holds if one marries a woman by means of money of hekdesh by accident she is married. That is a case of change of domain. But is it also deriving benefit from the money? I think the benefit in that case goes to the woman. So we now understand the Rambam. When the Jew buys from a gentile, he transgresses meila because the gentile has acquired the money immediately. But when he buys from a Jew neither party acquires anything until the buyer picks up the object.-------------------------------------------------------------------I tried to understand what רב שך and ר' אהרון קוטלר are saying about the subject in בבא מציעא מ''ח ע''אע. I cannot say I understand either. However, on the way back from the sea, it occurred to me what I think רב שך is saying. The רמב''ם wrote that when a Jew buys from a gentile (without picking up the object), and pays with money of הקדש, the Jew transgress מעילה, using money of the temple for secular benefit. But when the Jew buys from another Jew, and pays with money of הקדש (without picking up the object), he does not transgress meila. NOW רב שך asks on this, and I think he is asking that even when the Jew buys from another Jew, he should transgress the prohibition because from the law of the Torah money acquires. Now this is what I think about this. The decision of the Rambam is no problem because it is directly from the גמרא in עבודה זרה page 63. If one pays with a sheep to a prostitute that is a gentile, she acquire it even before she picks it up because money acquires, and the sex is in place of the money that pays for the sheep. This can also be considered to come directly from the גמרא in בבא מציעא page 48 because the ברייתא that רבא brings as support to ריש לקיש can easily be thought to refer to a gentile as תוספות writes there. The only question is what is the reasoning behind all this. According to the בעל המאור the law that a Jew acquires by means of pulling is for the benefit of the seller. The רמב''ן disagrees and hold it is for the benefit of both. But in either case it is for the benefit of the parties involved. Therefore, in the case where a Jew buys an object from a gentile, there is no decree off the sages for the benefit of the gentile. Therefore, he acquires the money that is paid to him immediately even if the Jew does not acquire the object until he picks it up (as the מהר''ם from לובלין writes in עבודה זרה page ס''ג. Therefore, the Jew transgress מעילה immediately because the money has gone out of the domain of הקדש. And even though רב שך brings from אחרונים that the רמב''ם does not hold with change of domain, still there is plenty of evidence that he does. For example, he holds if one marries a woman by means of money of הקדש by שוגג she is married. That is a case of change of domain. But is it also deriving benefit from the money? I think the benefit in that case goes to the woman. So we now understand the רמב''ם. When the Jew buys from a gentile, he transgresses מעילה because the gentile has acquired the money immediately. But when he buys from a Jew neither party acquires anything until the buyer picks up the object.