Straighten your rows for the straightening of the rows is part of perfecting the prayer.
Sunan Abi Dawud Book 2, Hadith 278
← Previous Hadith The Prophet (ﷺ) said: Stand close together in your rows, bring them near one another, and stand neck to neck, for by Him in Whose hand my soul is, I see the devil coming in through openings in the row just like a small black sheep.

Sunan Abi Dawud Book 2, Hadith 277 Next Hadith → one day I prayed by the side of Anas b. Malik. He said ; Do you know why this stick is placed here ? I said : No, by Allah. He said; The Messenger of Allah (ﷺ) used to put his hand upon it and say: Keep straight and straighten your rows.

Sunan Abi Dawud Book 2, Hadith 279