"The Messenger of Allah ﷺ came out to us and said:'Will you not form rows as the angels form rows before their Lord? They said: 'How do the angels form rows before their lord? He said: 'They complete the first row and fill the gaps in the rows."' (Using translation from Nasāʾī 816)
خَرَجَ رَسُولُ اللهِ ﷺ إِلَى الصُّفُوفِ فَقَالَ أَلَا تَصُفُّونَ كَمَا تَصُفُّ الْمَلَائِكَةُ عِنْدَ رَبِّهِمْ؟ قَالُوا وَكَيْفَ تَصُفُّ الْمَلَائِكَةُ عِنْدَ رَبِّهِمْ؟ قَالَ يُتِمُّونَ الصُّفُوفَ الْمُقَدَّمَةَ وَيَتَرَاصُّونَ فِي الصَّفِّ