Why do you stand in rows as the angels do in the presence of their Lord? We asked: how do the angles stand in rows in the presence of their Lord? He replied: they make the first row complete and keep close together in the row.
Sunan Abi Dawud Book 2, Hadith 271
← Previous Hadith we used to pray along with the Messenger of Allah (ﷺ) in intense heat. When any of us could not rest his face on bare ground while prostrating due to intense heat he spread his cloth and would prostrate on it.

Sunan Abi Dawud Book 2, Hadith 270 Next Hadith → 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.

Sunan Abi Dawud Book 2, Hadith 272