Narrated Abdullah ibn Amr ibn al-'As:
There are some expressions which a man utters three times when he gets up from an assembly he will be forgiven for what happened in the assembly; and no one utters them in an assembly held for a noble cause or for remembrance of Allah but that is stamped with them just as a document is stamped with a signet-ring. These expressions are: Glory be to You, O Allah, and I begin with praise of You, there is no god but you; I ask Your pardon, and return to You in repentance.