The Prophet (ﷺ) said, "Straighten your rows for I see you from behind my back." Anas added, "Everyone of us used to put his shoulder with the shoulder of his companion and his foot with the foot of his companion."
Sahih al-Bukhari Book 10, Hadith 119
← Previous Hadith I arrived at Medina and was asked whether I found any change since the days of Allah's Messenger (ﷺ). I said, "I have not found any change except that you do not stand in alignment in your prayers."

Sahih al-Bukhari Book 10, Hadith 118 Next Hadith → I prayed with the Prophet (ﷺ) one night and stood on his left side. Allah's Messenger (ﷺ) caught hold of my head from behind and drew me to his right and then offered the prayer and slept. Later the Mu'adh-dhin came and the Prophet (ﷺ) stood up for prayer without performing ablution.

Sahih al-Bukhari Book 10, Hadith 120