The Book of Mosques and Places of Prayer
5/23. Chapter:
The remembrance after the prayer
Sahih Muslim
حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنْ عَمْرٍو، قَالَ أَخْبَرَنِي بِذَا أَبُو مَعْبَدٍ، - ثُمَّ أَنْكَرَهُ بَعْدُ - عَنِ ابْنِ عَبَّاسٍ، قَالَ كُنَّا نَعْرِفُ انْقِضَاءَ صَلاَةِ رَسُولِ اللَّهِ صلى الله عليه وسلم بِالتَّكْبِيرِ .
Ibn 'Abbas said: We used to know that Allah's Messenger (ﷺ) had finished his prayer when we heard the takbir (Allah-O-Akbar).
Reference : Sahih Muslim 583aIn-book reference : Book 5, Hadith 154USC-MSA web (English) reference : Book 4, Hadith 1209