عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلّى الله عليه وسلّم قَالَ: سَوُّوا صُفُوفَكُمْ فَإِنَّ تَسْوِيَةَ الصُّفُوفِ مِنْ إِقَامَةِ الصَّلاَةِ
Hazrat Anasra narrated that the Prophetsa said: “Straighten your rows, for indeed, aligning the rows is part of establishing the prayer.”
(Sahih al-Bukhari, Kitab al-adhan, Bab iqamati s-saffi min tamami s-salah, Hadith 723)