Sahih Muslim Book - 4, Hadith - 1061

وَحَدَّثَنِى أَبُو بَكْرِ بْنُ نَافِعٍ الْعَبْدِىُّ حَدَّثَنَا بَهْزٌ حَدَّثَنَا حَمَّادٌ أَخْبَرَنَا ثَابِتٌ عَنْ أَنَسٍ قَالَ مَا صَلَّيْتُ خَلْفَ أَحَدٍ أَوْجَزَ صَلاَةً مِنْ صَلاَةِ رَسُولِ اللَّهِ -صلى الله عليه وسلم- فِى تَمَامٍ كَانَتْ صَلاَةُ رَسُولِ اللَّهِ -صلى الله عليه وسلم- مُتَقَارِبَةً وَكَانَتْ صَلاَةُ أَبِى بَكْرٍ مُتَقَارِبَةً فَلَمَّا كَانَ عُمَرُ بْنُ الْخَطَّابِ مَدَّ فِى صَلاَةِ الْفَجْرِ وَكَانَ رَسُولُ اللَّهِ -صلى الله عليه وسلم- إِذَا قَالَ « سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ ». قَامَ حَتَّى نَقُولَ قَدْ أَوْهَمَ. ثُمَّ يَسْجُدُ وَيَقْعُدُ بَيْنَ السَّجْدَتَيْنِ حَتَّى نَقُولَ قَدْ أَوْهَمَ.

It was narrated that Anas said: "I have never prayed behind anyone who made the prayer so brief yet perfect as the Messenger of Allah (s.a.w) did. The prayer of the Messenger of Allah (s.a.w) was well balanced. And the prayer of Abu Bakr was well balanced, too. During the time of 'Umar bin Al-Khattab, he made the Fajr prayer lengthy. But when the Messenger of Allah (s.a.w) said: 'Sami'a Allahu liman hamidah,' he would stand for so long that we would think, he has forgotten. Then he would prostrate, and he would sit for so long between the two prostrations that would we think he has forgotten."