How has the practice of reading the dua "Allahumma antassalamu wa minkassalam,.." after prayer has been? What is the practice of the Messenger of Allah regarding the issue like?

Dear Brother / Sister,

The following is stated in a hadith reported by Thawban: When the Prophet (pbuh) saluted, - according to another narration - when he finished prayer, he would say "astaghfirullah" three times and " Allahumma antassalamu wa minkassalam, tabarakta ya dhal jalali wal ikram (O Allah, You are Peace and from You is Peace. Blessed are You, O Possessor of Glory and Generosity)."

This dua is said after fard prayers but it can also be said after sunnah prayers. For, the loftiness of Allah, who is the possessor of glory, is remembered. From this point of view, it is sunnah to read it after sunnah prayers too. 

It is definite by hadiths of the Prophet (pbuh) and it is sunnah to say "astaghfirullah" three times, "Allahumma antassalamu,.." subhanallah, alhamdulillah, Allahu akbar 33 times after fard prayers and to read ayatul-kursi and even the chapters of al-Falaq and an-Nas.

However, they were not pronounced aloud and with the instruction of the muezzin during the time of the Prophet (pbuh); everybody used to say and read them silently. When those who did not know Arabic and prayer started to become Muslims, the muezzins started to say them aloud in order to teach them. Then, it became a habit and to remind them was regarded as a duty of the muezzin.

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