Full Sharh — Bulugh al-Maram 391
وَعَنْ ثَوْبَانَ - رضى الله عنه - قَالَ : { كَانَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -إِذَا اِنْصَرَفَ مِنْ صَلَاتِهِ اِسْتَغْفَرَ اَللَّهَ ثَلَاثًا , وَقَالَ : " اَللَّهُمَّ أَنْتَ اَلسَّلَامُ وَمِنْكَ اَلسَّلَامُ . تَبَارَكْتَ يَا ذَا اَلْجَلَالِ وَالْإِكْرَامِ } رَوَاهُ مُسْلِمٌ . 11 - صحيح . رواه مسلم ( 591 ) ، وزاد : قال الوليد : فقلت للأوزاعي : كيف الاستغفار ؟ قال : تقول : استغفر الله . استغفر الله .
English Translation
Narrated Thauban (RA):: Whenever Allah's Messenger (ﷺ) finished his prayer, he used to say after asking Allah's forgiveness three times: "O Allah, You are as-Salam (One Free from every defect), and as-Salam (safety from every evil) is (sought) from You. Blessed are You, O Possessor of glory and honour." .
Source
Bulugh al-Maram(بلوغ المرام)
The Book of Prayer
Hadith Number
391