Muwatta Malik #1479

Yahya related to me from Malik from Hisham ibn Urwa from his father from Zaynab bint Abi Salama from Umm Salama, the wife of the Prophet, may Allah bless him and grant him peace, that the Messenger of Allah, may Allah bless him and grant him peace, said, "I am but a man to whom you bring your disputes. Perhaps one of you is more eloquent in his proof than the other, so I give judgement according to what I have heard from him. Whatever I decide for him which is part of the right of his brother, he must not take any of it, for I am granting him a portion of the Fire."