Shias are those who believe in the right of the Ahlulbait in the religious leadership after the Prophet (peace be upon him) because they believe that the latter ordered Muslims to follow the Ahlulbaitt and refer to them after his death. This idea was explained by many texts, one of them is the tradition of Al-Thaqalain in which the Prophet said: "I leave among you the two weighty things, the book of Allah and my progeny; as long as you are attached to them both, you will never be misguided". The said tradition is widely recognized in the Shia and Sunnis books of traditions. Similar to this is the tradition of Al-Ghadeer and other narrations as well.
A number of companions of the Prophet (peace be upon him) believed in this faith and defended it, like Salman, Abu Dharr, Ammar, Hudhaifa and others.
This ideology remained in all different stages of Islamic history without any change.

The beliefs of Sunnis are not different than those of Shias with respect to the belief in the two testimonies. The difference is in the concept of Imamate – the leadership of the nation of Islam after the death of the Prophet (peace be upon him and his holy progeny) – where the followers of the Ahlulbait (peace be upon them) believe in the Imams from the Ahlulbait as the religious and the political leaders of the Muslim nation after the Prophet (peace be upon him and his holy progeny), as this is mentioned in a very clear and frank way in the tradition of Thaqalain. It is reported in the books of traditions of Shias and Sunnis that the Prophet said: "I leave among you the two weighty things, the book of Allah and my progeny; as long as you follow both of them, you will never be misguided".