Musnad Abu Ya'la al-Mawsili 42:115

Sarij narrated to us, Abu Hafs al-Abbar narrated to us, from Muhammad ibn Jahadah, from Atiyyah, from Abu Sa’id, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The people who will receive the severest punishment on the Day of Resurrection are a tyrannical leader."