“I said to abu ‘Abdallah (a.s.). “If something would happen (death of Imam), may Allah will not make me experience it, then who must I follow as my Imam?” The narrator has said that he pointed to his son Musa (a.s.). I then asked, “What if something will happen to Musa (a.s.) then who must I follow as my Imam?” The Imam (a.s.) said, “Follow his sons. Then he said, “In this way for ever.” I then asked, “What if I will not know him and will not know his place?” The Imam (a.s.) said, “Say, ‘O Lord, I love and take as my guardian whoever is left (on earth) as your authority of the sons of the preceding Imam. This will be enough for you if Allah would so will.”