Hazrat Abu Al-Bakhtari says that I and Hazrat Ubaidah were passing through the mosque when Hazrat Mus'ab was leading the people in prayer. When he finished the prayer, he said in a loud voice: There is no deity except Allah, Allah is the Greatest. Upon hearing this, Hazrat Ubaidah said: May Allah destroy them, these are the people who act upon the innovation of announcing aloud, this is the innovation of Ali (may Allah be pleased with him).