Musnad Abu Ya'la al-Mawsili 2:22

Mus'ab ibn 'Abd Allah narrated to us, Ibn al-Darawardi narrated to us, from Muhammad ibn Abi Humayd, from Zayd ibn Aslam, from his father, from 'Umar, who said: The Messenger of Allah (ﷺ) said: "Shall I not inform you of the best of your leaders from the worst of them? Those whom you love and they love you, and they pray for you and you pray for them. And the worst of your leaders are those whom you hate and they hate you, and you curse them and they curse you."