AAaishah رضي الله عنها said: Whenever The Messenger of Allah (SAWS) 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 (SAWS), 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.’
سُبْحـانَكَ وَبِحَمدِك، لا إِلهَ إِلاّ أَنْتَ أَسْتَغْفِرُكَ وَأَتوبُ إِلَـيْك.
Subhanaka wabihamdik, la ilaha illa anta astaghfiruka wa-atoobu ilayk.
‘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.’