Abu Barzah (May Allah be pleased with him) reported:
Towards the end of his life, Messenger of Allah ﷺ would supplicate before leaving an assembly thus: "Subhanaka Allahumma wa bihamdika, ash-hadu an la ilaha illa Anta, astaghfiruka wa atubu ilaika (O Allah, You are free from every imperfection; all praise is for You. I testify that there is no true god except You, I ask Your forgiveness and turn to You in repentance).'' A man once said to him: "O Messenger of Allah! You have spoken such words as you have never uttered before.'' He said, "It is an expiation of that which goes on in the assembly.''

[Abu Dawud].

وعن أبى برزة رضى الله عنه قال: كان رسول الله ﷺ يقول بآخرة إذا أراد أن يقوم من المجلس: "سبحانك الله وبحمدك، أشهد أن لا إله إلا أنت، أستغفرك وأتوب إليك" فقال رجل: يا رسول الله، إنك لتقول قولاً ما كنت تقوله فيما مضى؟ قال: "ذلك كفارة لما يكون في المجلس" (3).