Sunan An Nasai
1167
It was narrated from Al-Aswad and 'Alqamah, that Abdullah bin Mas'ud said:
We were with the Messenger of Allah (ﷺ) and we did not know anything, then the Messenger of Allah (ﷺ) said to us: Every time you sit (in prayer), say: At-tahiyyatu..
READ COMPLETE