Musannaf Ibn Abi Shayba 13:1217

Abu Bakr narrated to us, he said: Ibn Idris narrated to us, from al-Shaybani, from al-Sha’bi, from Shurayh: Regarding a man who returns a slave due to a disease, he said: He returns him, and he (the buyer) is entitled to the profit (generated by the slave).