Imam (a.
Imam (a.s.) said: May Allah’s mercy be on you. Had it been so that after the revelation of this verse to someone that person died and, after him, there would not have been anyone to know the meaning of this verse and to make this command applicable to the people, verily the Book of Allah would have become dead, that is, meaningless and its command would have been suspended.
But the Book of Allah is alive till Qiyamat, that is, the Divine Command, through the agreement of the Ummah, is to exist till Qiyamat and the duty imposed by Allah is never lifted up from or cancelled for the people and if there is no such conveyer of Divine commands who is sinless (never erring) and if anyone else explains the Divine command to the people the Book of Allah will be rendered fruitless and if duty remains it will entail ignorance and it is injustice and Allah never commits injustice.
This is one of the clear arguments, which makes it essential that Allah has to appoint an Imam. Ibne Babawayh has, in his book, Akmaluddeen , authentically quoting Imam Baqir (a.s.) while explaining the verse (13:7) writes that it means Imams who are the guides of people in their times in which they live.
And certainly We have made the word to reach them so that they may be mindful… (Sura Qasas 28:51) That is We joined for them one verse after another and one story after another and the promise with the warning and the admonishments through stories which may provide lessons to them so that they may obtain advice.
In this connection many narrations are recorded from the Ahlul Bayt (a.s.) to explain that it means the appointment of one Imam after another as Ali Ibne Ibrahim has mentioned in his commentary and by Shaykh Tusi in Majalis with authentic chains. He has said that, explaining this verse; Imam Sadiq (a.s.) said that it means that We appointed one Imam after another. There are some probabilities in this explanation.
First: it might mean that We, by appointing one Imam after another, applied the word, that is, statement of Truth and the propagation of the truthful commands and codes, to the people.