the prophet ﷺ used to straighten us in the rows of prayer as the arrow is straightened, until he thought that we had learned it from him and understood it. One day he turned towards us, and shoulders in order, and say; Do not be irregular. And he would say: Allah and his Angels bless those who near the first rows. (Using translation from Abū Dāʾūd 663)   

كَانَ رَسُولُ اللهِ ﷺ يُسَوِّينَا فِي الصُّفُوفِ كَمَا تُقَوَّمُ الْقِدَاحُ حَتَّى ظَنَّ أَنَّا قَدْ أَخَذْنَا ذَلِكَ عَنْهُ وَفَهِمْنَاهُ وَأَقْبَلَ ذَاتَ يَوْمٍ بِوَجْهِهِ فَإِذَا رَجُلٌ مُنْتَبِذٌ بِصَدْرِهِ فَقَالَ لَتُسَوُّنَّ صُفُوفَكُمْ أَوْ لَيُخَالِفَنَّ اللهُ بَيْنَ وُجُوهِكُمْ  

“The Messenger of Allah ﷺ used to straighten the rows until he made them like a spear or an arrow-shaft. Once he saw a man’s chest (sticking out) so the Messenger of Allah ﷺ said: ‘Make your rows straight or Allah will create division among you.’” (Using translation from Ibn Mājah 994)   

سَمِعْتُ النُّعْمَانَ بْنَ بَشِيرٍ وَهُوَ يَخْطُبُ وَيَقُولُ كَانَ رَسُولُ اللَّهِ ﷺ يُسَوِّي الصَّفَّ حَتَّى يَدَعَهُ مِثْلَ الْقِدْحِ أَوِ الرُّمْحِ فَرَأَى صَدْرَ رَجُلٍ نَاتِئًا مِنَ الصَّفِّ فَقَالَ «عِبَادَ اللَّهِ لَتُسَوُّنَّ صُفُوفَكُمْ أَوْ لَيُخَالِفَنَّ اللَّهُ بَيْنَ وُجُوهِكُمْ»