Abu Dawud

661. Commentary:
➊ By standing close together in the row, the row becomes straight.
➋ It is understood that adopting the actions of the righteous is legislatively desirable, and a Muslim should always be eager to resemble them—especially in matters of forming rows in prayers. In Surah Al-Fatihah, this very supplication has been taught: «اهدنا الصراط المستقيم . صراط الذين انعمت عليهم»
➌ The first row should be completed first, then the second should be formed.

Benefits and Issues:
➊ In Islamic Shariah, the methods of worship are similar to the methods by which the angels worship. And this is a great honor.

➋ The angels stand in rows to worship Allah.

➌ Until the first row is completed, the second row should not be started. In this way, after the second, the third row should be formed, and after the third, the fourth row.

➍ When standing in a row, one should stand close together. There should not be an empty space left between two people. The noble Companions (radi Allahu anhum ajma'in) used to stand shoulder to shoulder and foot to foot with each other. See: (Sahih al-Bukhari, al-Adhan, Chapter: Joining shoulder to shoulder and foot to foot in the row, Hadith: 725)

Benefit:
From this hadith, it is understood that at the end of the prayer, when saying "As-salamu alaykum wa rahmatullah," one should not gesture with the hands to the right and left, but rather should keep the hands on the thighs while saying the salam. Some people have made a great mistake by trying to prove non-raising of the hands from this hadith, whereas this hadith clearly states that the noble Companions (radi Allahu anhum ajma'in) used to move their hands to the right and left when saying the salam. But unfortunately, blind following is the enemy of the Qur'an and Hadith, and in the eyes of the follower (muqallid), respect is for his own imam, not for the Qur'an and Hadith.