Whenever Allah’s Messenger (ﷺ) finished his prayer, he used to say Allahumma antas salam dua after asking Allah’s forgiveness three times: [Reported by Muslim].
اللَّهُمَّ أَنْتَ السَّلاَمُ وَمِنْكَ السَّلاَمُ تَبَارَكْتَ يَا ذَا الْجَلاَلِ وَالإِكْرَامِ
Transliteration: Allahumma Antas-Salam wa minkas-salam. Tabarakta ya Dhal-jalali wal- ikram.
“O Allah, You are As-Salam, From You is all peace, blessed are You O Possessor of majesty and honour”
It’s said for the following reasons:
Act of Worship glorifying Allah.
Shows remembrance of Allah subhanahu wa ta’ala.
The All-Loving 