Sahih Bukhari 721

Narrated Abu Huraira: The Prophet said, The Imam is (appointed) to be followed. So do not differ from him, bow when he bows, and say, Rabbana-lakal hamd if he says Sami`a l-lahu liman hamidah ; and if he prostrates, prostrate (after him),..

Narrated Anas bin Malik: The Prophet said, Straighten your rows as the straightening of rows is essential for a perfect and correct prayer. ..

Narrated Anas bin Malik: I arrived at Medina and was asked whether I found any change since the days of Allah's Apostle. I said, I have not found any change except that you do not stand in alignment in your prayers. ..

Narrated Anas bin Malik: The Prophet 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. ..

Narrated Ibn `Abbas: I prayed with the Prophet one night and stood on his left side. Allah's Apostle 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 stood..

Narrated Anas bin Malik: One night an orphan and I offered the prayers behind the Prophet in my house and my mother (Um Sulaim) was standing behind us (by herself forming a row). ..