Tractate Bava Metzia, page 48 side a. Tractate Avoda Zara, page 63 side a. And Tosphot and Rav Shach.

Tosphot asks what is the difference between meila and etnan? For meila we have the din in Bava Meztia money acquires [he gave money of hekdesh to a large store he transgresses meila], but for a etnan only pulling acquires. I mentioned beforehand that to the Rambam this is no question. When it comes to a gentile, money acquires, and those cases in Bava Metzia are referring to a gentile. But, Tosphot asks this, and gives an answer that is hard to understand. Rav Shach uses the idea of the Baal HaMeor in order to explain Tosphot. When it comes to meila, all we need is for the bathhouse owner or the retail store to acquire. But for the sheep to be an etnan, we need there to be the impossibility of nullifying the deal since etnan requires not just acquisition, but also that the giving of it should be final. [After the act of sex, that part of the deal cannot be nullified, but he can pay for it, and thus he can nulify the acquisition of the sheep.]]-------------------תוספות (עבודה זרה דף ס''ג)asks what is the difference between מעילה and אתנן? For מעילה we have the דין in בבא מציעא money acquires [ אם he gave money of הקדש to a retail store, he transgresses מעילה], but for a אתנן only משיכה acquires. I mentioned beforehand that to the רמב''ם ,this is no question. When it comes to a gentile, money acquires, and those cases in בבא מציעא מ''ח ע''א are referring to a gentile. But, תוספות asks this, and gives an answer that is hard to understand. רב שך uses the idea of the בעל המאור in order to explain תוספות. When it comes to מעילה, all we need is for the bathhouse owner בלןor the סיטון to acquire. But for the sheep to be an אתנן, we need there to be the impossibility of nullifying the deal since אתנן requires not just acquisition, but also that the giving of it should be final. [After the act of sex, that part of the deal cannot be nullified, but he can pay for it, and thus he can nulify the acquisition of the sheep.]---To rava in bava metzia to trangrssss meila one needs only change of domain and therefoe that braita (he gave it to a bath-hous keeper transgresses only because no need for pulling or picking up).----------------- But according to the Rambam, R Yochanan holds one needs only to derive benefit from the hekdesh in order to transgresses meila, therefore that braita is no question. Also, buying from a gentile transgresses because he derives benefit, but if he buys from a Jew without picking up the object, no sale has gone through, and so there is no benefit as the Or Sameach pointed out.------------------But according to the רמב''ם, ר' יוחנן holds one needs only to derive benefit from the הקדש in order to transgresses מעילה, therefore that ברייתא is no question. Also, buying from a gentile transgresses because he derives benefit, but if he buys from a Jew without picking up the object, no sale has gone through, and so there is no benefit as the אור שמח pointed out.