الكافي 2/1/51/5

5. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad ibn ‘Isa from al-Hassan ibn Mahbub from abu Kahmas who has said the following: “Once I said to Abu ‘Abdillah عليه السلام “Abd Allah ibn abu Ya’fur has sent you ( salam ) greetings.’ The Imam said, ‘May salam (peace) be with you and with him. If you meet ‘Abd Allah convey salam to him and say, ‘Ja’far, son of Muhammad, says to you, “Consider to what level Ali (Amir al-Mu’minin ibn abu Talib) had reached before the Messenger of Allah. You must follow his manners. Ali عليه السلام reached the level that he reached before the Messenger of Allah because of the truthfulness in his words and his trustworthiness in returning the trust.’””