Kaffarat al-Majlis: Expiation of whatever negative may have occurred in a gathering

When the Messenger of Allah ﷺ intended to get up from the assembly he used to say toward the end:

subḥānak Allāhummā wa-bi-ḥamdika, ash-hadu an lā ilāha illā anta, astaghfiruka wa-atūbu ilayka

(Glory be to You. O Allah and with Your praise, I testify that there is no god but You; I seek Your forgiveness, and turn to Your in repentance.)

A 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.

كَانَ رَسُولُ اللَّهِ ﷺ يَقُولُ بِأَخَرَةٍ إِذَا أَرَادَ أَنْ يَقُومَ مِنَ الْمَجْلِسِ:

(سُبْحَانَكَ اللَّهُمَّ وَبِحَمْدِكَ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ أَنْتَ أَسْتَغْفِرُكَ وَأَتُوبُ إِلَيْكَ)

فَقَالَ رَجُلٌ يَا رَسُولَ اللَّهِ إِنَّكَ لَتَقُولُ قَوْلاً مَا كُنْتَ تَقُولُهُ فِيمَا مَضَى قَالَ كَفَّارَةٌ لِمَا يَكُونُ فِي الْمَجْلِسِ