الكافي 1/4/126/13

13. Through the same chain of narrators the following is narrated: “Amir al-Mu’minin عليه السلام one day said to Abu Bakr, “Do not think of those slain for the cause of God as dead. They are alive with their Lord and receive sustenance from Him.” (3:169) I testify that Muhammad the Messenger of Allah صلى الله عليه وعلى آله وسلم died as a martyr. He by Allah, will come to you and do have any doubts when he will come to you. Satan can not appear in his disguise.” Ali عليه السلام took the hand of Abu Bakr and showed the Prophet صلى الله عليه وعلى آله وسلم to him who said to him, “O Abu Bakr, believe in Ali and in the eleven Imams from his descendants. They are all like me except prophethood. Repent before Allah because of what you involvement in what you are involved. You have no right in it.” The narrator has said that then he went and was not seen around.”