This Is My Faith - Al-fatlawi, Ali - الصفحة ٢٨٩ - The Details of the Two Conceals (Al-Ghaibah)
that the Imam (AHHR) is a living person and that he did his responsibility, namely saying prayer over the previous deceased Imam.
This proves that he is the next Imam and he must be obeyed. As a matter of fact, Imam Al-Mahdi (PBUH) stood up to deviation and allegation of his uncle, Ja’far Bin Ali, and began his guidance and direction to his supporters and followers.
His Minor Conceal started in the year ٢٦٠ AH when the ruling regime went after the Imam (AHHR). During his Conceal, he was contacting his Ambassadors whom he placed as his agents. The Major Conceal started with the death of the fourth and the last Ambassador. There are more details in this regard, but this serves the purpose.
Anwar: Now that we know the Imam (AHHR) is in his Major Conceal, I would like to ask about the reasons for the Conceal.
Hasan: I clarified that the ruling regime at the time was in pursuit of Imam Al-Mahdi (AHHR) in order to kill him. This is the main reason. I will briefly mention the other reasons: