Musnad Abu Ya'la al-Mawsili 3:304

Al-Qawariri narrated to us, Muhammad bin Ubayd Allah al-Abdi narrated to us, from Hafs bin Khalid al-Abdi, my father narrated to me, from my grandfather, from Ali, that the Messenger of Allah (may Allah bless him and grant him peace) addressed the people one day and said: "Beware, the leaders are from Quraysh. Beware, the leaders are from Quraysh. Beware, the leaders are from Quraysh, as long as they uphold three things: as long as they judge and are just, and as long as they make a covenant and fulfill it, and as long as they are asked for mercy and they show mercy. Whoever among them does not do that, then upon him is the curse of Allah, the angels, and all of mankind."