عَنْ أُبَيِّ بْنِ كَعْبٍ رَضِيَ اللَّهُ عَنْهُ أَنَّهُ قَالَ: صَلَّى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ الصُّبْحَ فَقَالَ: ((شَاهِدٌ فُلَانٌ؟)) فَقَالُوا: لَا، فَقَالَ: ((شَاهِدٌ فُلَانٌ؟)) فَقَالُوا: لَا، فَقَالَ: ((شَاهِدٌ فُلَانٌ؟)) فَقَالُوا: لَا، فَقَالَ: ((إِنَّ هَاتَيْنِ الصَّلَاتَيْنِ مِنْ أَثْقَلِ الصَّلَوَاتِ عَلَى الْمُنَافِقِينَ، وَلَوْ يَعْلَمُونَ مَا فِيهِمَا لَأَتَوْهُمَا وَلَوْ حَبْوًا، وَالصَّفُّ الْمُقَدَّمُ عَلَى مِثْلِ صَفِّ الْمَلَائِكَةِ، وَلَوْ تَعْلَمُونَ فَضِيلَتَهُ لَابْتَدَرْتُمُوهُ، وَصَلَاةُ الرَّجُلِ مَعَ الرَّجُلَيْنِ أَزْكَى مِنْ صَلَاتِهِ مَعَ رَجُلٍ، وَمَا كَانَ أَكْثَرَ فَهُوَ أَحَبُّ إِلَى اللَّهِ تَعَالَى))
It is narrated from Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) led the morning prayer and then said: "Is such-and-such a man present?" The people said: "No." Then he (peace and blessings be upon him) said: "Is such-and-such a man present?" The people said: "No." Then he (peace and blessings be upon him) said: "Is such-and-such a man present?" The people said: "No." Then the Messenger of Allah (peace and blessings be upon him) said: "Indeed, these two prayers (Isha and Fajr) are very burdensome upon the hypocrites. If they knew what reward lies in them, they would surely come to perform them, even if they had to crawl on their buttocks. And the first row is like the row of angels, and if you knew its virtue, you would try to outdo one another to attain it. And the prayer performed by a man with two others is purer (i.e., has more reward) than the prayer performed with one man, and the more people there are, the more beloved that prayer is to Allah."