Jami` at-Tirmidhi 298
جامع الترمذي#298SahihAishah narrated:"When Allah's Messenger said the Salam he would not remain seated except long enough to say: (Allahumma antas-salam, wa minkas-salam, tabarakta dhal jalali wal-Ikram) 'O Allah! You are the One free of defects, and perfection is from You. Blessed are You, Possessor of Majesty and Honor
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 2:150