Musannaf Ibn Abi Shayba 13:388

Jarir narrated to us, from al-‘Ala’, from Hammad, from Ibrahim, who said: If I came to a governor and he gave me a gift, I would accept it from him. It is merely in the position of the public treasury (Bayt al-Mal); the impure and the pure enter it. And he said: If a messenger comes to you regarding a matter of disobedience, then there is no good in his gift. And if he comes to you regarding a matter in which there is no harm, then there is no harm in his gift.