Sunan of Abu Dawood Book 2, Hadith 554

حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي بَصِيرٍ، عَنْ أُبَىِّ بْنِ كَعْبٍ، قَالَ صَلَّى بِنَا رَسُولُ اللَّهِ صلى الله عليه وسلم يَوْمًا الصُّبْحَ فَقَالَ ‏"‏ أَشَاهِدٌ فُلاَنٌ ‏"‏ ‏.‏ قَالُوا لاَ ‏.‏ قَالَ ‏"‏ أَشَاهِدٌ فُلاَنٌ ‏"‏ ‏.‏ قَالُوا لاَ ‏.‏ قَالَ ‏"‏ إِنَّ هَاتَيْنِ الصَّلاَتَيْنِ أَثْقَلُ الصَّلَوَاتِ عَلَى الْمُنَافِقِينَ وَلَوْ تَعْلَمُونَ مَا فِيهِمَا لأَتَيْتُمُوهُمَا وَلَوْ حَبْوًا عَلَى الرُّكَبِ وَإِنَّ الصَّفَّ الأَوَّلَ عَلَى مِثْلِ صَفِّ الْمَلاَئِكَةِ وَلَوْ عَلِمْتُمْ مَا فَضِيلَتُهُ لاَبْتَدَرْتُمُوهُ وَإِنَّ صَلاَةَ الرَّجُلِ مَعَ الرَّجُلِ أَزْكَى مِنْ صَلاَتِهِ وَحْدَهُ وَصَلاَتُهُ مَعَ الرَّجُلَيْنِ أَزْكَى مِنْ صَلاَتِهِ مَعَ الرَّجُلِ وَمَا كَثُرَ فَهُوَ أَحَبُّ إِلَى اللَّهِ تَعَالَى ‏"‏ ‏.‏

Narrated Ubayy ibn Ka'b: The Messenger of Allah (ﷺ) led us in the dawn prayer one day. And he said: Is so and so present? They said: No. He (again) asked: Is so and so present? They replied: No. He then said: These two prayers are the ones which are most burdensome to hypocrites. If you knew what they contain (i.e. blessings), you would come to them, even though you had to crawl on your knees. The first row is like that of the angels, and if you knew the nature of its excellence, you would race to join it. A man's prayer said along with another is purer than his prayer said alone, and his prayer with two men is purer than his prayer with one, but if there are more it is more pleasing to Allah, the Almighty, the Majestic