Musannaf Ibn Abi Shayba 23:61

Muhammad ibn Bishr narrated to us, he said: Muhammad ibn ‘Amr narrated to us, from Abu Salamah, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The most complete of the believers in faith, and the most excellent of the believers in faith, are those of them who are best in character."