Hazrat A'mash says that Ibrahim was asked: If the Imam, after saying salam, says "Sallallahu 'ala Muhammad" or "La ilaha illallah," what is the ruling on this? He replied: The predecessors did not use to do so.

Hazrat Abu Al-Bakhtari says that this is an innovation (bid'ah).

Hazrat Umar bin Abdul Aziz says that the perfection of prayer is that after completing the prayer, you say these words three times: There is no deity except Allah, He is alone, He has no partner. Sovereignty belongs to Him and all praise is for Him. And He has power over everything.