Mon Nedarim 43

Someone took an oath not to take pleasure from a person, neither can lend to each other, nor borrow from each other nor buy from each other.

The Gemara asks, I understand why the oath maker can't borrow since he receives pleasure from him. However, why can't he lend?

Abaya's answers that we make a Gezeira that if he lends he'll come to borrow.

The Ran asks: that it seems all over that only the one who makes the oath can't have pleasure from the other person, but the second person may have pleasure from the oath maker, and we don't decree to forbid him?

The Ran answers: when dealing with regular pleasures, like eating from the second person, we know that it's included in the oath, so there is no reason someone will get mixed up. However, the pleasures listed in the Mishna are not such strong pleasures that one might mistake that it's not included in the oath. So if the second person will borrow from the oath maker, they'll make a mistake thinking that it's not included, and the oath maker may borrow. Therefore they enacted it in this situation.