Musnad Ahmad 1302:5

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, he said: I heard al-Qasim ibn Abi Bazzah, from 'Ata' al-Kaykharani, from Umm al-Darda', from Abu al-Darda', that the Messenger of Allah, may Allah bless him and grant him peace, said: "There is nothing heavier in the scale than good character."