Sahih Muslim Book 020, Hadith Number 4502.
Chapter : The merits of a just ruler and the demerits of a tyrant ruler.
It has been narrated on the authority of Abu Malik that Ubaidullah b. Ziyad visited Ma'qil b. Yaser in the latter's illness. Ma'qil said to him: I am narrating to you a tradition. If I were not at death's door, I would not narrate it to you. I heard the Messenger of Allah (may peace he upon him) say: A ruler who, having obtained control over the affairs of the Muslims, does not strive for their betterment and does not serve them sincerely shall not enter Paradise with them.