Also he (the Prophet) has ordered me to order you that when death comes to you...
Also he (the Prophet) has ordered me to order you that when death comes to you, give them (the books and the weapon) to your brother al-Husayn." Then Imam 'Ali turned to al-Husayn and said: "The Apostle of Allah has ordered you to give them to this son of you." [1] Then he took the hand of 'Ali b. al-Husayn and said: "The Apostle of Allah has ordered you to give them to your son Muhammad. Send him the greetings of the Apostle of Allah and my (greetings).
[2] All tradition books have mentioned this tradition through authentic reliable chains of narrations on the authority of the members of the House (Ahl alBayt), peace be on them. This tradition of 'Ali was appropriate for the expected conditions. The Imami Shi'a use this method to prove the Imamate. The Sunni scholars have reported successive Prophetic traditions through their methods. Also non- Sunni scholars have clearly reported the same traditions through their methods.
They (the traditions) have limited the Imamate to twelve Imams who were all from Quraysh. [3] Also they some times mention their names Imam by Imam to the last one of them, who is the awaited Mahdi (the rightly guided one), with whom Allah will fill the earth with justice when it is full of oppression and injustice. [1] Al-Mas'udi, Hamish b. al-Athir, vol. 6, 61. [2] 'Usul al-Kafi, p. 151. Kashf al-Ghumma, p.159. [3] In his book called 'al-Sahih, vol.2, p.
119, Chapter: People were the Followers of Quraysh, Muslim has reported on the authority of Jabir b. Samra, who said: "I (i.e., Jabir) heard the Apostle of Allah, may Allah bless him and his family, saying: 'The religion will last till the hour (i.e., the Day of Judgment) starts, and there will be twelve Imams over them (people), who are all from Quraysh.'" A similar tradition has been reported by: al-Bukhari, al-Tirmidhi, al-Hamidi, and the like.
Moreover, there are personal texts which the imams said to nominate each other. Then the supremacy of each imam in knowledge, acts, miracles, and outstanding merits underlines both kinds of the above- mentioned traditions. As for the pledge of allegiance of people, it is not a condition in the imamate of the Imam. In other words, people should pledge allegiance to those whom the Prophetic traditions have underlined. The Imamis regard pledging allegiance to other than the Imam as a correct act.
It (pledging allegiance) is not accepted from anyone but at the time of compulsion.