Jami` at-Tirmidhi 300
جامع الترمذي#300Sahihحَدَّثَنَا أَحْمَدُ بْنُ مُحَمَّدِ بْنِ مُوسَى، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ الْمُبَارَكِ، أَخْبَرَنَا الأَوْزَاعِيُّ، حَدَّثَنِي شَدَّادٌ أَبُو عَمَّارٍ، حَدَّثَنِي أَبُو أَسْمَاءَ الرَّحَبِيُّ، قَالَ حَدَّثَنِي ثَوْبَانُ، مَوْلَى رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا أَرَادَ أَنْ يَنْصَرِفَ مِنْ صَلاَتِهِ اسْتَغْفَرَ اللَّهَ ثَلاَثَ مَرَّاتٍ ثُمَّ قَالَ " اللَّهُمَّ أَنْتَ السَّلاَمُ وَمِنْكَ السَّلاَمُ تَبَارَكْتَ يَا ذَا الْجَلاَلِ وَالإِكْرَامِ " . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ . وَأَبُو عَمَّارٍ اسْمُهُ شَدَّادُ بْنُ عَبْدِ اللَّهِ .
Thawban, the freed slave of Allah's Messenger, narrated that :Allah's Messenger said: "When Allah's Messenger wanted to turn from his Salat, he would seek forgiveness from Allah three times, then say: (Allahumma Antas-Salam, wa minkas-salam, tabarakta ya dhal-jalali wal-Ikram) 'O Allah! You are the One free of defects and perfection is from You. Blessed are You, O Possesor of Majesty and Honor
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 2:152