Abul Hasan Ali ibn Muhammad al-Samarri

In Twelver Shia Islam, Abul Hasan Ali ibn Muhammad al-Samarri was the fourth and last of The Four Deputies appointed by the twelfth and final Imam, Muhammad al-Mahdi, while he was in the Minor Occultation. Unlike his predecessors he had no appointed successor, and the Major Occultation began after his death.

He was a companion of the 11th Shia Imam Hasan al-Askari and was designated as the fourth and last of The Four Deputies for a period of 3 years after the death of the third deputy Abul Qasim Husayn ibn Ruh al-Nawbakhti. Six days before his death, he received a letter from the twelfth and final Imam, Muhammad al-Mahdi, in which he was notified that there would be no deputy after him. A translation of the letter is as follows:

"In the name of Allah, the Compassionate the Merciful

O Ali Ibn Muhammad Samari! May Allah increase the reward of your brothers concerning you (i.e. your demise)! Death will come to you within the next six days. So you complete your works and do not nominate any person after you. The sequence of special deputies will come to an end and the Major Occultation (غيبت كبرى) will commence with your demise.

Now the reappearance will occur only with the permission of Allah, after a prolonged period and after the hearts of people are hardened. And such a period will emerge on my Shias when people will claim that they have seen me. Whoever makes such a claim before the advent of Sufyani and the heavenly voice, is a liar, an impostor. There is no strength and power save that of Allah, the High, the Great.”

On the sixth day after receiving the letter, Abul Hasan Ali ibn Muhammad al-Samarri died (329 AH) and he was buried in Baghdad near the current grave of Sheikh Kulayni. Before his death, they asked him about the next deputy and he responded: "I don't have permission to introduce anyone".

Following his death, the Major Occultation began.