حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ النُّفَيْلِيُّ، حَدَّثَنَا زُهَيْرٌ، قَالَ سَأَلْتُ سُلَيْمَانَ الأَعْمَشَ عَنْ جَابِرِ بْنِ سَمُرَةَ، فِي الصُّفُوفِ الْمُقَدَّمَةِ فَحَدَّثَنَا عَنِ الْمُسَيَّبِ بْنِ رَافِعٍ، عَنْ تَمِيمِ بْنِ طَرْفَةَ، عَنْ جَابِرِ بْنِ سَمُرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَلاَ تَصُفُّونَ كَمَا تَصُفُّ الْمَلاَئِكَةُ عِنْدَ رَبِّهِمْ جَلَّ وَعَزَّ ‏"‏ ‏.‏ قُلْنَا وَكَيْفَ تَصُفُّ الْمَلاَئِكَةُ عِنْدَ رَبِّهِمْ قَالَ ‏"‏ يُتِمُّونَ الصُّفُوفَ الْمُقَدَّمَةَ وَيَتَرَاصُّونَ فِي الصَّفِّ ‏"‏ ‏.‏

This tradition has also ben transmitted by Anas through a different chain of transmitters. This version goes

when the Messenger of Allah (ﷺ) stood for prayer, he took it (the stick) in his right hand and turning (to the right side) said; keep straight and straighten your rows. He then took it in his left hand and said; keep straight and straighten your rows.