"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 إِلَيْنَا رَسُولُ اللهِ ﷺ فَقَالَ «أَلَا تَصُفُّونَ كَمَا تَصُفُّ الْمَلَائِكَةُ عِنْدَ رَبِّهِمْ؟» قَالُوا وَكَيْفَ تَصُفُّ الْمَلَائِكَةُ عِنْدَ رَبِّهِمْ؟ قَالَ «يُتِمُّونَ الصَّفَّ الْأَوَّلَ وَيَتَرَاصُّونَ فِي الصَّفِّ»