It was narrated from Aishah that : the Messenger of Allah (ﷺ) ruled that what a slave earns belongs to his guarantor
It was narrated from 'Aishah that: a man bought a slave and put him to work, then he found some defect in him, so he returned him. He (the seller) said: O Messenger of Allah he put my slave to work. The Messenger of Allah (ﷺ) said: A slave's earnings belong to his guarantor.