عَنْ سَيَّارِ بْنِ الْمَعْرُورِ قَالَ: سَمِعْتُ عُمَرَ وَهُوَ يَخْطُبُ يَقُولُ: إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ بَنَى هَٰذَا الْمَسْجِدَ وَنَحْنُ مَعَهُ الْمُهَاجِرُونَ وَالْأَنْصَارُ فَإِذَا اشْتَدَّ الزِّحَامُ فَلْيَسْجُدِ الرَّجُلُ مِنْكُمْ عَلَى ظَهْرِ أَخِيهِ، وَرَأَى قَوْمًا يُصَلُّونَ فِي الطَّرِيقِ فَقَالَ: صَلُّوا فِي الْمَسْجِدِ
Sayyar bin Ma’rur says: I heard Sayyiduna ‘Umar (may Allah be pleased with him) delivering a sermon, and he was saying: Indeed, the Messenger of Allah (peace and blessings be upon him) built this mosque, while we, the Muhajirun and Ansar, were with him (peace and blessings be upon him). So when the crowd becomes large, a person should prostrate on the back of his brother. Then Sayyiduna ‘Umar (may Allah be pleased with him) saw some people praying on the road and said to them: Pray in the mosque.