Al-Nu’man b. Bashir said: 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.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا حَمَّادٌ، عَنْ سِمَاكِ بْنِ حَرْبٍ، قَالَ سَمِعْتُ النُّعْمَانَ بْنَ بَشِيرٍ، يَقُولُ كَانَ النَّبِيُّ صلى الله عليه وسلم يُسَوِّينَا فِي الصُّفُوفِ كَمَا يُقَوَّمُ الْقِدْحُ حَتَّى إِذَا ظَنَّ أَنْ قَدْ أَخَذْنَا ذَلِكَ عَنْهُ وَفَقِهْنَا أَقْبَلَ ذَاتَ يَوْمٍ بِوَجْهِهِ إِذَا رَجُلٌ مُنْتَبِذٌ بِصَدْرِهِ فَقَالَ " لَتُسَوُّنَّ صُفُوفَكُمْ أَوْ لَيُخَالِفَنَّ اللَّهُ بَيْنَ وُجُوهِكُمْ " .
sunnah.com