Mishkat al-Masabih 4 Prayer كتاب الصلاة 514

وَعَنِ النُّعْمَانِ بْنِ بَشِيرٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُسَوِّي صُفُوفَنَا إِذَا قُمْنَا إِلَى الصَّلَاةِ فَإِذَا اسَتْوَيْنَا كَبَّرَ. رَوَاهُ أَبُو دَاوُد

An-Nu‘man b. Bashir said: God’s Messenger used to straighten our rows when we stood up to pray, and when we were straight he said, “God is most great.” Abu Dawud transmitted it.