Sahih Bukhari Volume 3, Book 31, Hadith 2011

وَعَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ عَبْدٍ الْقَارِيِّ، أَنَّهُ قَالَ خَرَجْتُ مَعَ عُمَرَ بْنِ الْخَطَّابِ ـ رضى الله عنه ـ لَيْلَةً فِي رَمَضَانَ، إِلَى الْمَسْجِدِ، فَإِذَا النَّاسُ أَوْزَاعٌ مُتَفَرِّقُونَ يُصَلِّي الرَّجُلُ لِنَفْسِهِ، وَيُصَلِّي الرَّجُلُ فَيُصَلِّي بِصَلاَتِهِ الرَّهْطُ فَقَالَ عُمَرُ إِنِّي أَرَى لَوْ جَمَعْتُ هَؤُلاَءِ عَلَى قَارِئٍ وَاحِدٍ لَكَانَ أَمْثَلَ‏.‏ ثُمَّ عَزَمَ فَجَمَعَهُمْ عَلَى أُبَىِّ بْنِ كَعْبٍ، ثُمَّ خَرَجْتُ مَعَهُ لَيْلَةً أُخْرَى، وَالنَّاسُ يُصَلُّونَ بِصَلاَةِ قَارِئِهِمْ، قَالَ عُمَرُ نِعْمَ الْبِدْعَةُ هَذِهِ، وَالَّتِي يَنَامُونَ عَنْهَا أَفْضَلُ مِنَ الَّتِي يَقُومُونَ‏.‏ يُرِيدُ آخِرَ اللَّيْلِ، وَكَانَ النَّاسُ يَقُومُونَ أَوَّلَهُ‏

'Abdur Rahman bin 'Abdul Qari said, "I went out in the company of 'Umar bin Al-Khattab one night in Ramadan to the mosque and found the people praying in different groups. A man praying alone or a man praying with a little group behind him. So, 'Umar said, 'In my opinion I would better collect these (people) under the leadership of one Qari (Reciter) (i.e. let them pray in congregation!)'. So, he made up his mind to congregate them behind Ubai bin Ka'b. Then on another night I went again in his company and the people were praying behind their reciter. On that, 'Umar remarked, 'What an excellent Bid'a (i.e. innovation in religion) this is; but the prayer which they do not perform, but sleep at its time is better than the one they are offering.' He meant the prayer in the last part of the night. (In those days) people used to pray in the early part of the night."