Sahih Muslim Book 18, Hadith Number 4247.

Chapter : Judgment is to be pronounced on evidence, and one who is eloquent in his plea (may win the case).

Umm Salama reported Allah’s Messenger (may peace be upon him) as saying: You bring to me, for (judgment) your disputes, some of you perhaps being more eloquent in their plea than others, so I give judgment on their behalf according to what I hear from them, (Bear in mind, in my judgment) if I slice off anything for him from the right of his brother, he should not accept that, for I sliced off for him a portion from the Hell.