(26) باب اسْتِحْبَابِ الذِّكْرِ بَعْدَ الصَّلاَةِ وَبَيَان صِفَتِهِ
Thauban reported:
When the Messenger of Allah (ﷺ) finished his prayer. He begged forgiveness three times and said: O Allah! Thou art Peace, and peace comes from Thee; Blessed art Thou, O Possessor of Glory and Honour. Walid reported: I said to Auza'i: How is the seeking of forgiveness? He replied: You should say: I beg forgiveness from Allah, I beg forgiveness from Allah."
Reference: Sahih Muslim 591
In-book reference: Book 5, Hadith 171
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1226