Musannaf Ibn Abi Shayba 13:1141

Abu Bakr narrated to us, he said: 'Abbad bin al-'Awwam narrated to us, from Yahya bin Sa'id, from Salim: That Ibn 'Umar sold a slave of his for eight hundred. The buyer found a defect in him, so he disputed with him before 'Uthman. 'Uthman asked him, and he said: "I sold him with [a condition of] immunity." 'Uthman said: "Swear by Allah that you sold him while there was no defect in him that you knew of." He said: "I sold him with [a condition of] immunity," and he refused to swear. So 'Uthman returned him to him, and he sold him after that for one thousand and five hundred.