The same message was sent to the second Caliph by Aisha...
The same message was sent to the second Caliph by Aisha, the Prophet's wife, begging him to appoint a successor. Could we claim that the two had realized the significance of the issue of leadership, but the Prophet had not realized the gravity of such an act?! A glimpse on the life of the Prophet will reveal the fact that he was always concerned with this issue; during his ten year stay in Medina, he never left this town without appointing a temporary substitute for himself.
He did not want the people to be without a leader in his absence. Is it fair then to say that such a prophet had not said anything concerning his successor when he had been so sensitive to such an issue? The Prophet would select a governor for any place or location which he captured. Then how could we claim that the Prophet had ignored such an important issue?
Imamate and prophethood are two sides of the same coin Frequent narrations and the history of Imamate attest to the fact that the prophethood and Imamate were announced to people on the same day: the day when the Prophet was assigned to announce his prophethood to his relatives was the same day as he appointed his substitute.
After praising God and admitting His uniqueness, he said: I am God's messenger for you and for all nations. I have brought blessings for you, valuable for both this life and the Hereafter. My God has ordered me to invite you to this religion and anybody among you who can help me will be my successor. At this moment, nobody rose to support the Prophet except for Ali Ibn Abi Talib. The Prophet ordered Ali to sit down. At that time, the Prophet repeated his statement two or three times.
Again no one rose in support apart from Ali (as). At this time the Prophet, addressing his relatives, declared “إنَّ هذا أخي و وصيي و خليفتي فيكم، فاسمعوا و أطيعوا” “Ali is my brother and my successor among you.