ENOfficial
Thauban said that when God’s Messenger finished his prayer he asked forgiveness three times and said, “O God, Thou art Peace, and peace comes from Thee. Blessed art Thou, O Possessor of glory and honour.” Muslim transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ ثَوْبَانَ رَضِيَ اللَّهُ عَنْهُ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا انْصَرَفَ مِنْ صَلَاتِهِ اسْتَغْفَرَ ثَلَاثًا وَقَالَ: «اللَّهُمَّ أَنْتَ السَّلَامُ وَمِنْكَ السَّلَامُ تَبَارَكْتَ يَا ذَا الْجلَال وَالْإِكْرَام» . رَوَاهُ مُسلم
sunnah.com