Musannaf Ibn Abi Shayba 13:85

Hushaym narrated to us, from Mughira, who said: I asked Ibrahim and al-Sha'bi about a man who had a slave who would pay him five [dirhams] every month. He said [to the slave]: "Give me two hundred dirhams every month, and I will give you nine dirhams every month." He said: They both saw no harm in that.