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كتاب الأذان
10
Call to Prayers (Adhaan)
(155)
Chapter: The Dhikr (remembering Allah by Glorifying, Praising and Magnifying Him) after As-Salat (the prayer)
(155)
باب الذِّكْرِ بَعْدَ الصَّلاَةِ
Sahih al-Bukhari 841

Narrated Abu Ma`bad:

(the freed slave of Ibn `Abbas) Ibn `Abbas told me, "In the lifetime of the Prophet (ﷺ) it was the custom to celebrate Allah's praises aloud after the compulsory congregational prayers." Ibn `Abbas further said, "When I heard the Dhikr, I would learn that the compulsory congregational prayer had ended."

حَدَّثَنَا إِسْحَاقُ بْنُ نَصْرٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ، قَالَ أَخْبَرَنَا ابْنُ جُرَيْجٍ، قَالَ أَخْبَرَنِي عَمْرٌو، أَنَّ أَبَا مَعْبَدٍ، مَوْلَى ابْنِ عَبَّاسٍ أَخْبَرَهُ أَنَّ ابْنَ عَبَّاسٍ ـ رضى الله عنهما ـ أَخْبَرَهُ أَنَّ رَفْعَ الصَّوْتِ بِالذِّكْرِ حِينَ يَنْصَرِفُ النَّاسُ مِنَ الْمَكْتُوبَةِ كَانَ عَلَى عَهْدِ النَّبِيِّ صلى الله عليه وسلم‏.‏ وَقَالَ ابْنُ عَبَّاسٍ كُنْتُ أَعْلَمُ إِذَا انْصَرَفُوا بِذَلِكَ إِذَا سَمِعْتُهُ‏.‏
Reference : Sahih al-Bukhari 841
In-book reference : Book 10, Hadith 233
USC-MSA web (English) reference : Vol. 1, Book 12, Hadith 802
  (deprecated numbering scheme)