Dhikr (mentioning the name of Allah) in a loud voice after obligatory prayers was (a common practice) during the lifetime of the Messenger of Allah ﷺ ; and when I heard that I came to knew that they (the people) had finished the prayer.
أَخْبَرَهُ أَنَّ رَفْعَ الصَّوْتِ بِالذِّكْرِ حِينَ يَنْصَرِفُ النَّاسُ مِنَ الْمَكْتُوبَةِ كَانَ عَلَى عَهْدِ النَّبِيِّ ﷺ وَأَنَّهُ قَالَ قَالَ ابْنُ عَبَّاسٍ كُنْتُ أَعْلَمُ إِذَا انْصَرَفُوا بِذَلِكَ إِذَا سَمِعْتُهُ
(the freed slave of Ibn ʿAbbas) Ibn ʿAbbas 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 ʿAbbas further said, "When I heard the Dhikr, I would learn that the compulsory congregational prayer had ended."
أَخْبَرَهُ أَنَّ رَفْعَ الصَّوْتِ بِالذِّكْرِ حِينَ يَنْصَرِفُ النَّاسُ مِنَ الْمَكْتُوبَةِ كَانَ عَلَى عَهْدِ النَّبِيِّ ﷺ وَقَالَ ابْنُ عَبَّاسٍ كُنْتُ أَعْلَمُ إِذَا انْصَرَفُوا بِذَلِكَ إِذَا سَمِعْتُهُ
To raise the voice for making the mention of Allah after the people had finished their obligatory prayer was for in vogue the time of the Messenger of Allah (May peace be upon him). Ibn ‘Abbas said : I used to know by it when they finished the prayer and would listen to it (making the mention of Allah).
أَخْبَرَهُ أَنَّ رَفْعَ الصَّوْتِ لِلذِّكْرِ حِينَ يَنْصَرِفُ النَّاسُ مِنَ الْمَكْتُوبَةِ كَانَ ذَلِكَ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ وَأَنَّ ابْنَ عَبَّاسٍ قَالَ كُنْتُ أَعْلَمُ إِذَا انْصَرَفُوا بِذَلِكَ وَأَسْمَعُهُ
(the freed slave of Ibn ʿAbbas) Ibn ʿAbbas 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 ʿAbbas further said, "When I heard the Dhikr, I would learn that the compulsory congregational prayer had ended." (Using translation from Bukhārī 841)
أَخْبَرَهُ أَنَّ رَفْعَ الصَّوْتِ بِالذِّكْرِ حِينَ يَنْصَرِفُ النَّاسُ مِنَ الْمَكْتُوبَةِ كَانَ عَلَى عَهْدِ النَّبِيِّ ﷺ وَأَنَّهُ قَالَ قَالَ ابْنُ عَبَّاسٍ كُنْتُ أَعْلَمُ إِذَا انْصَرَفُوا بِذَلِكَ إِذَا سَمِعْتُهُ
[Machine] "Raising the voice with remembrance when finished with the written (portion)" Did the Prophet ﷺ do it? Ibn Abbas said, "I knew that when I heard it."
«رَفْعُ النَّاسِ الصَّوْتَ بِالذِّكْرِ عِنْدَ الْفَرَاغِ مِنَ الْمَكْتُوبَةِ» كَانَ النَّبِيُّ ﷺ يَفْعَلُهُ؟ قَالَ ابْنُ عَبَّاسٍ «كُنْتُ أَعْلَمُ بِهِ إِذَا سَمِعْتُهُ»
"عَنِ ابْنِ عبَّاس: أَنَّ رَفْعَ الصَّوْت بِالذِّكْر حِينَ يَنْصَرِفُ النَّاسُ منَ الْمَكْتُوبَة كَانَ عَلَى عَهْدِ النَّبِىِّ ﷺ قَالَ ابْنُ عَبَّاس: كنتُ أَعْلَمُ إِذا انْصَرَفُوا بِذَلِكَ إِذَا سَمعْتُهُ".