It is sunnah of the Prophet Muhammad (ﷺ) to recite the full allahumma antas salam dua after taslim, that is after saying As-salamu alaykum warahmatullah at end of prayer.
This does not mean that you must say this dua, it is not obligatory. The purpose of this dua is better understood once you understand the meaning of this dua. It’s said for the following reasons:
- Act of Worship glorifying Allah.
- Shows remembrance of Allah subhanahu wa ta’ala.
- Re-affirms one’s faith.
Full Dua in Arabic:
In Arabic text the full allahumma antas salam dua would be,
اللَّهُمَّ أَنْتَ السَّلاَمُ وَمِنْكَ السَّلاَمُ تَبَارَكْتَ يَا ذَا الْجَلاَلِ وَالإِكْرَامِ
Transliteration: Allahumma Antas-Salam wa minkas-salam. Tabarakta ya Dhal-jalali wal- ikram.
Allahumma Antas Salam Dua – English Translation:
“O Allah, You are As-Salam, From You is all peace, blessed are You O Possessor of majesty and honour”
Reference:
This dua is referenced in different hadiths of Ibn Majah, At-Tirmidhi, and An-Nasa’i. It is graded as authentic or Sahih (Darussalam).