Musnad Ahmad 733:1

Hassan ibn Musa narrated to us, Ibn Lahi'ah narrated to us, Bakr ibn Sawadah narrated to us, from Ubayd Allah ibn Aslam, the freed slave of the Prophet, may Allah bless him and grant him peace, that the Messenger of Allah, may Allah bless him and grant him peace, used to say to Ja'far ibn Abi Talib: "You have resembled my physical appearance and my character."