Hadithcore
Mishkat al-Masabih, 960

‘A’isha said that when God’s Messenger uttered the salutation he sat no longer than it took to say, “O God, You are Peace, and peace comes from You. Blessed are You, O Possessor of glory and honour.” Muslim transmitted it.

وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا سَلَّمَ لَمْ يَقْعُدْ إِلَّا مِقْدَارَ مَا يَقُولُ: «اللَّهُمَّ أَنْتَ السَّلَامُ وَمِنْكَ السَّلَامُ تَبَارَكْتَ يَا ذَا الْجلَال وَالْإِكْرَام» . رَوَاهُ مُسلم

References1 variant
In-Book Reference
Book 4, Hadith 383