We do not say except that which our Lord, Most High, has said He said: Abu Hafs Umar b. Muhammad al-Sayrafi reported to me from Muhammad b. Hammam al-Askafi who reported from Ahmad b. Idrees, who reported from Ahmad b. Muhammad b. Isa al-Asha'ri, from Ali b. No-man, from Fudhail b. Uthman, from Muhammad b. Shurayh who said:
I heard Abu Abdillah Ja'far b. Muhammad, peace be upon him, say: "Surely, ALLAH (SWT) has enforced our authority, and made it obligatory upon people to love us. By ALLAH (SWT), we do not say anything out of caprice or our desire, and we do not act according to our views. We do not say except that which our Lord, Most High, has said."
(Ref: Al-Amali Shaikh Mufeed: The Seventh Assembly : Hadees No.4)