Musannaf Ibn Abi Shayba 33:113

Ibn Fudayl narrated to us, from Layth, from ‘Amr ibn Murrah—Jarir added from Mu’awiyah ibn Suwayd—from al-Bara’ ibn ‘Azib, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The firmest handhold of faith is love for the sake of Allah and hatred for the sake of Allah."