when the Messenger of Allah (ﷺ) stood for prayer, he took it (the stick) in his right hand and turning (to the right side) said; keep straight and straighten your rows. He then took it in his left hand and said; keep straight and straighten your rows.
Sunan Abi Dawud Book 2, Hadith 280
← Previous 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 Next Hadith → The Prophet (ﷺ) said: Complete the front row, then the one that comes next, and if there is any incompleteness, let it be in the last row.

Sunan Abi Dawud Book 2, Hadith 281