And (as for) those who believe and their offspring follow them in faith...
And (as for) those who believe and their offspring follow them in faith, We will unite with them their offspring and We will not diminish to them aught of their work; every man is responsible for what he shall have wrought. (Sura Tur 52:21) It is narrated that it is popular opinion among the commentators that this verse is about the children of the believers whom Allah will admit to Paradise along with their parents and forefathers. This explanation is mentioned in our commentary also.
Say: We believe in Allah and (in) that which had been revealed to us, and (in) that which was revealed to Ibrahim and Ismail and Ishaq and Yaqoob and the tribes, and (in) that which was given to Musa and Isa, and (in) that which was given to the prophets from their Lord, we do not make any distinction between any of them, and to Him do we submit. (Sura Baqarah 2:136) That is we have not discriminated against anyone of them and we are obedient to Allah.
So if they also believe as you have believed then doubtlessly they are rightly guided and if they deviate and disbelieved then they are in the state enmity and envy. Then, O Messenger! Allah will protect you from their evil and He hears and knows everything.
Kulaini, Ayyashi and others have narrated from Imam Baqir (a.s.) that, in this verse, ‘Say’ is the address to the Aale Muhammad, that is, to Ali, Fatima, Hasan and Husain and thereafter the Imams from their progeny and condition of ‘if they believe’ means all other people. It is essential that their faith should be like the faith of the Imams and they should also follow them in beliefs and actions (deeds). Most commentators have opined that the address of ‘Say’ is to all the faithful people.