When the Prophet ﷺ uttered taslim, he used to say: "O Allah, You are As-Salam, and from you is As-Salam. You are blessed, O One of Magnificence and Generosity." (Using translation from Abū Dāʾūd 1512)  

أَنَّ رَسُولَ اللهِ ﷺ كَانَ إِذَا سَلَّمَ قَالَ «اللهُمَّ أَنْتَ السَّلَامَ وَمِنْكَ السَّلَامُ تَبَارَكْتَ يَا ذَا الْجِلَالِ وَالْإِكْرَامِ»