Sahih Muslim Book 20, Hadith Number 4500.

Chapter : The merits of a just ruler and the demerits of a tyrant ruler.

It has been narrated on the authority of Hasan who said: Ubaidullah b Ziyad visited Ma’qil b. Yasir al-Muzani in his last illness. Ma’qil said (to him): I am narrating to you a tradition I heard from the Messenger of Allah (may peace be upon him). If I knew that I am to survive this illness. I would, not narrate it to you. I heard the Messenger of Allah (may peace be upon him) say: If God appointed anyone ruler over a people and he died while he was still treacherous to his people, God would forbid his entry into Paradise.