Musannaf Ibn Abi Shayba 13:2813

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Zakariya ibn Abi Za’idah narrated to us, from ‘Amir, he said: I asked him about a man who lends a man dirhams, and he is given back better than them. He said: There is no harm in it, as long as he does not intend it or stipulate it.