Hadith #4859 (Sunan Abi Dawud)
Book: General Behavior (Kitab Al-Adab)
Narrator(s): Abdullah bin 'Amr bin al-Faghwa' عبد الله بن عمرو بن الفغواء, Amr bin al-Faghwa', Ibn Ishaq محمد بن إسحاق بن يسار‎, Ibrahim bin Sa'd bin Ibrahim إبراهيم بن سعد بن إبراهيم, Isa bin Ma'mr Hjazy عيسى بن معمر حجازي, Muhammad bin Yahya bin Faris al-Dhahli محمد بن يحيى بن فارس الذهلي, Nwh bin Yazid bin Syar نوح بن يزيد بن سيار البغدادي
Grade: Hasan Sahih

When the Messenger of Allah (ﷺ) intended to get up from the assembly he used to say in the last. Glory be to Thee. O Allah, and I begin with praise of Thee, I testify that there is no god but Thou; I ask Thy pardon, and return to Thee 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.

Source: https://parallelquran.com/hadith/sunan-abi-dawud-4859/