Musannaf Ibn Abi Shayba 13:1328

Abu Bakr narrated to us, he said: Jarir narrated to us, from Mughira, from al-Harith al-'Ukli, who said: If a man buys two slave boys or two items, and finds a defect in one of them, and wishes to return it, he returns it for its value, and the one that has no defect remains binding upon him.