(Imām Bukhārī narrates): Ishāq ibn Nasr narrated to us, he said: 'Abdur-Razzāq narrated to us, he said: Ibn Juraij informed us, he said: 'Amr informed me that Abū Ma'bad, the freed slave of Ibn 'Abbās, informed him that Ibn 'Abbās, may Allāh be pleased with them both, informed him that:
in the time of the Messenger of Allāh ﷺ, it was the practice of the people that they would remember Allāh the Exalted after finishing the prayer. Ibn 'Abbās said: When I heard this remembrance, I would know that the people had finished the prayer.
Reference: Sahih Al Bukhari 841