"The Messenger of Allah ﷺ used to straighten the rows like shaft of an arrow is straightened before the head is attached to it. He saw a man whose chest was sticking out from the row. I saw the Messenger of Allah ﷺ say: 'Make your rows straight or Allah will cause your faces to be deformed." (Using translation from Nasāʾī 810)  

كَانَ رَسُولُ اللهِ ﷺ يُقَوِّمُ الصُّفُوفَ كَمَا تُقَوَّمُ الْقِدَاحُ فَأَبْصَرَ رَجُلًا خَارِجًا صَدْرُهُ مِنَ الصَّفِّ فَلَقَدْ رَأَيْتُ النَّبِيَّ ﷺ يَقُولُ «لَتُقِيمُنَّ صُفُوفَكُمْ أَوْ لَيُخَالِفَنَّ اللهُ بَيْنَ وُجُوهَكُمْ»  

"The Messenger of Allah ﷺ used to go between the rows from one side to another, patting our shoulders and chests and saying: 'Do not make your rows ragged or your hearts will be filled with enmity toward one another.' And he used to say: 'Allah and His angels send Salah upon the front rows."' (Using translation from Nasāʾī 811)  

كَانَ رَسُولُ اللهِ ﷺ يَتَخَلَّلُ الصَّفَّ مِنْ نَاحِيَتِهِ إِلَى نَاحِيَتِهِ يَمْسَحُ مَنَاكِبَنَا وَصُدُورَنَا وَيَقُولُ «لَا تَخْتَلِفُوا فَتَخْتَلِفَ قُلُوبُكُمْ» وَكَانَ يَقُولُ «إِنَّ اللهَ وَمَلَائِكَتَهُ يُصَلُّونَ عَلَى الصُّفُوفِ الْمُقَدَّمَةِ»