Mishkat al-Masabih 1085
An-Nu‘man b. Bashir said:
God’s Messenger used to straighten our rows as if he were trying to make them as straight as arrows until he saw that we had learned it from him. One day he came out, stood up, and was just about to say God is most great ’ when he saw a man whose chest projected from the row, so he said, “Servants of God, you must straighten your rows, or God will certainly put your faces in contrary directions."*

* The use of “faces” here may mean the people themselves and their inner nature. The tradition may refer to civil strife, which is possibly the meaning of the tradition below from Abu Mas'ud.

Muslim transmitted it.
عَن النُّعْمَانِ بْنِ بَشِيرٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُسَوِّي صُفُوفَنَا حَتَّى كَأَنَّمَا يُسَوِّي بِهَا الْقِدَاحَ حَتَّى رَأَى أَنَّا قَدْ عَقَلْنَا عَنْهُ ثُمَّ خَرَجَ يَوْمًا فَقَامَ حَتَّى كَادَ أَنْ يُكَبِّرَ فَرَأَى رَجُلًا بَادِيًا صَدْرُهُ مِنَ الصَّفِّ فَقَالَ: «عِبَادَ اللَّهِ لَتُسَوُّنَّ صُفُوفَكُمْ أَوْ لَيُخَالِفَنَّ اللَّهُ بَيْنَ وُجُوهِكُمْ» . رَوَاهُ مُسلم