(4) when hussein-ibn-ruh passed away, abul-hassan ali-ibn-muhammad seymouri succeeded him. none of these four deputies revolted for the post of special deputyship but was given to them by imam of the age himself. the shias would not have accepted the sayings of these four deputies but for the various evidences which each of them had at hand which substantiated their sayings.
when muhammad-ibn-ali seymouri's death approached he was asked about his immediate successor.
in this regard, a «tawqee» (signed letter) written by Mahdi (a.s.) himself was given out as a reply. the contents of this «tawqee» are as follows:-
in the name of god
o ali ibn muhammad seymouri! may Allah increase the reward of your brothers on account of the difficulties born by you. you will die within six days. so prepare yourself for the inevitable. do not appoint anyone as your successor because your demise will mark the beginning of the major occultation. i will not emerge but after a long time when the hearts of the people will become hardened and the world will become full of injustice, tyranny and oppression.
signed letters (from imam of the age) would be sent to them and they in turn would transfer wealth to his eminence. these deputies were many in number perhaps hundred, but they could not visit hazrat. as a matter of fact, the four afore-said deputies acted as the mediators between them and imam (a.s.).
kashi narrates: a 'tawqee' (signed letter) was sent for qasim-ibn-ala with such contents: whatever is narrated by the learned scholars upon whom we are having trust should never be doubted by our friends. this is because we have made them partners in our secret and we have entrusted our secrets to them....
shaikh tusi in 'ghaibat', shaikh saduq in 'kamaluddin' and tabarsi in 'ehtejaj' have narrated from ishaaq-ibn-ammar that Mahdi (a.s.) has said: 'but as for the problems which will arise in the future, you should refer to the narrators of our traditions for their verdicts as they are my proofs to you, and i am Allah's proof to them....