Musannaf Ibn Abi Shayba 13:2433

Abu Bakr narrated to us, he said: Abu Dawud al-Tayalisi narrated to us, from Shu'bah, who said: Al-Hakam said to me: Ibn Abi Layla came to me and asked me about a man who had a debt owed to him by another man, and he gifted it to him. Does he have the right to retract it? I said: No. And I asked Hammad, and he said: Yes, he has the right to retract it.