Sahih al-Bukhari 847
Sahih al-Bukhari · Book 10: Call to Prayers (Adhaan) · The Imam should face the followers after finishing the prayer with Taslim.
Narrated Anas bin Malik:
حَدَّثَنَا عَبْدُ اللَّهِ ، سَمِعَ يَزِيدَ ، قَالَ أَخْبَرَنَا حُمَيْدٌ ، عَنْ أَنَسٍ ، قَالَ أَخَّرَ رَسُولُ اللَّهِ صلى الله عليه وسلم الصَّلاَةَ ذَاتَ لَيْلَةٍ إِلَى شَطْرِ اللَّيْلِ ثُمَّ خَرَجَ عَلَيْنَا، فَلَمَّا صَلَّى أَقْبَلَ عَلَيْنَا بِوَجْهِهِ فَقَالَ " إِنَّ النَّاسَ قَدْ صَلَّوْا وَرَقَدُوا، وَإِنَّكُمْ لَنْ تَزَالُوا فِي صَلاَةٍ مَا انْتَظَرْتُمُ الصَّلاَةَ " .
Once the Prophet (ﷺ) delayed the `Isha' prayer until midnight and then came to us. Having prayed he faced us and said, "The people had prayed and slept but you were in the prayer as long as you were waiting for it."