Musannaf Ibn Abi Shayba 13:1337

Abu Bakr narrated to us, he said: Jarir narrated to us, from Mughira, from Hammad, who said: The *mudarib* (manager of the profit-sharing partnership) shall not stipulate food, nor anything from which he derives benefit, unless it contains a benefit for the *mudaraba* (the partnership). If it does not contain a benefit for the *mudaraba*, then that shall be at the expense of his own wealth.