(Mishnah): Three days before the festivals of the idolaters ('Eidehem'), it is prohibited to buy and sell from them (lest the Jew be the cause of the idolaters going and thanking their gods for the profits made); to lend or borrow items or money from them; to repay or collect loans.

(R. Yehuda): One may collect a loan from them because it is painful for them.

(Chachamim): Even though he is pained now, he is happy later.

(R. Yishmael): Both three days before and three days after are prohibited.

(Chachamim): Before is prohibited but after is permitted.

(Gemara): R. Chama bar Ukva learned this law of three days before, from the pasuk referring to when Jews were serving idols (Amos 4:4), "and bring your sacrifices in the morning, every three days your tithes". This is an allusion to the fact that the idolaters prepare their sacrifices for three days before their festival.

Question (R. Yosi to R. Chama): If the law is alluded to in the pasuk, then the law should apply even in the Diaspora, but the Baraisa taught - Nachum HaMadi says that these prohibitions only apply on the day that precedes the festival...?

Answer: What is Nachum HaMadi's reason? They discovered that the idolators prepared for the festival only on the day prior to it. However, here they checked and found that it was for three days, so they prohibited all three days.