Dua for For the expiation of sins, said at the conclusion of a sitting or gathering

Subhaanaka Allaahumma wa bihamdika, 'ash-hadu 'an laa 'ilaaha 'illaa 'Anta, 'astaghfiruka wa 'atoobu 'ilayka.

Glory is to You, O Allah, and praise is to You. I bear witness that there is none worthy of worship but You. I seek Your forgiveness and repent to You.(Allah's Messenger (SAW) did not sit in a gathering, and did not recite the Qur'an, and did not perform any prayer without concluding by saying this invocation.)