Supplication for the expiation of sins said at the conclusion of a sitting or gathering (and Supplication for concluding all sittings)

سُبْحَانَكَ اللَّهمَّ وَبِحَمْدِكَ، أَشْهَدُ أَنْ لا إِلَهََ إِلاَّ أَنْتَ أَسْتَغْفِرُكَ وَأَتُوْبُ إِلَيْكَ

‘How perfect You are O Allah, and I praise You. I bear witness that None has the right to be worshipped except You. I seek Your forgiveness and turn to You in repentance.’

سُبْحَانَكَ وَبِحَمْدِكَ، لا إِلَهَ إِلاَّ أَنْتَ أَسْتَغْفِرُكَ وَأَتُوْبُ إِلَيْكَ

Aisha (ra) said: Whenever The Messenger of Allah r would betake a seat, read Quran or pray, he would always conclude it with certain words, I (i.e. AAaishah) said: O Messenger of Allah r, I have noticed that whenever you betake a seat, read Quran or pray, you always conclude it with these words. He said: Yes, whoever speaks good, it (i.e. the supplication) will be a seal for that goodness and whoever speaks ill, it will be an atonement for him.’
‘How perfect You are and I praise You. None has the right to be worshipped except You, I seek Your forgiveness and turn in repentance to You.’