Short answer

Abu Bakr, Umar, Uthman and Ali, and, in the count of scholars such as Ibn Kathir, Ali's son al-Hasan. The Prophet (ﷺ) said the caliphate of prophecy would last thirty years. Ali himself walked the road this page invites us to follow. He gave his pledge to Abu Bakr and to Uthman, and he asked Allah's (﷾) mercy for Umar when his body was laid out. When the people pledged to him in turn, he took office the same way, and he told the people of Iraq to keep judging as before. His son al-Hasan then made the peace the Prophet (ﷺ) foretold. Following Ali means following what Ali did.

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