Narrated Abu Barzah al-Aslami:
When the Messenger of Allah (ﷺ) intended to get up from the assembly he used to say in the last. Glory be to You. O Allah, and I begin with praise of You, I testify that there is no god but You; I ask Your pardon, and return to You in repentance. The man asked: Messenger of Allah! you utter the words now which you did not do in the past? He replied: (This is an) atonement for what takes place in the assembly.