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.‏

 

Narrated Abu Ma`bad:
(the freed slave of Ibn `Abbas) Ibn `Abbas told me, “In the lifetime of the Prophet 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.” (Sahih Bukhari)

You know how we know the compulsory congregational prayer is over? We see people leaving the masjid and/or mussalla. They didn’t do that back then. SubhanAllah! Imagine if after the salah at a masjid, everyone begin to make dhikr outloud. It would be looked down upon as biddah by some.