Sahih Bukhari Volume 1, Book 10, Hadith 848

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 ‏"

Narrated By Anas bin Malik : Once the Prophet 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."