It was narrated that `Asim bin Damrah said:
We came to `Ali bin Abi Talib (رضي الله عنه) and said: O Ameer al-Mu`mineen, why don`t you tell us about the voluntary prayer of the Messenger of Allah (ﷺ)? He said: Who among you can do that? They said: We will take what we can do. He said: The Messenger of Allah (ﷺ) used to pray sixteen rak`ahs during the day apart from the Prescribed prayers.