Shi'ah which means literally partisan or follower, refer to those who consider the succession to the Prophet – may God's peace and benediction be upon him – to be the special right of the family of the Prophet and who in the field of the Islamic sciences and culture follow the school of the Household of the Prophet.

The Holy Prophet during the first days of his prophecy, when according to the text of the Quran he was commanded to his closer relatives to come to his religion, told them clearly that whoever would be the first to accept his invitation would become his successor and inheritor. Ali was the first to step forth and embrace Islam. The Prophet accepted Ali's submission to the faith and thus fulfilled his promise.

From the Shi'ite point of view it appears as unlikely that the leader of a movement, during the first days of his activity, should introduce to strangers one of his associates as his successor and deputy but not introduce him to his completely loyal and devout aides and friends. Nor does it appear likely that such a leader should accept someone as his deputy and successor and introduce him to others as such, but then throughout his life and religious call deprive his deputy of his duties as deputy, disregard the respect due to his position as successor, and refuse to make any distinction between him and others.

The Prophet, according to many unquestioned and completely authenticated hadiths, both Sunni and Shi'ite, clearly asserted that Ali was preserved from error and sin in his actions and sayings. Whatever he said and did was in perfect conformity with the teaching of religion and he was the most knowledgeable of men in matters pertaining to the Islamic sciences and injunction.