Language:
كتاب الأذان
10
Call to Prayers (Adhaan)
(74)
Chapter: The straightening of the rows is amongst those obligatory and good things which make your As-Salat (the prayer) a correct and perfect one.
(74)
باب إِقَامَةِ الصَّفِّ مِنْ تَمَامِ الصَّلاَةِ

Narrated Anas bin Malik:

The Prophet (ﷺ) said, "Straighten your rows as the straightening of rows is essential for a perfect and correct prayer. "

حَدَّثَنَا أَبُو الْوَلِيدِ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ سَوُّوا صُفُوفَكُمْ فَإِنَّ تَسْوِيَةَ الصُّفُوفِ مِنْ إِقَامَةِ الصَّلاَةِ ‏"‏‏.‏
Reference : Sahih al-Bukhari 723
In-book reference : Book 10, Hadith 117
USC-MSA web (English) reference : Vol. 1, Book 11, Hadith 690
  (deprecated numbering scheme)