سنن أبي داود

Al-Nu’man b. Bashir said: the Messenger of Allah (ﷺ) paid attention to the people and said three times; straighten your rows (in prayer); by Allah, you must straighten your rows, or Allah will certainly put your faces in contrary directions. I then saw that every person stood in prayer keeping his shoulder close to that of the other, and his knee close to that of the other, and his ankle close to that of the other.