Musannaf Ibn Abi Shaybah

Hazrat Zuhri says regarding the person who sold a slave in exchange for goats, then those goats gave birth and the number of goats increased, then a defect was found in the slave which had been concealed from him, he said: He will return the slave, and he will have to give goats of the same kind, or return them in the same condition as he had received.