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
← Previous Hadith 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 Next Hadith → The Prophet (ﷺ) said: The best of you are those whose shoulders are soft in prayer.

Sunan Abi Dawud Book 2, Hadith 282