Narrated by Anas Bin Malik:

The Prophet Muhammad (saws) said, "Straighten your rows for I see you from my back".

Anas added, "Everyone of us used to put his shoulder with the shoulder of his companion and his foot with the foot of his companion."

(Hadith No. 692, vol. 1, Book 11 - Sahih Bukhari)

Narrated by An-Numan Bin Bashir:

The Prophet Muhammad (saws) said, "Straightened your rows or Allah will alter your faces."

(Hadith No. 685, Vol. 1 Book 11- Sahih Bukhari)

Narrated by Anas Bin Malik:

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

(Hadith No. 690, vol. 1, Book 11 Sahih Bukhari)