(Attributed hadith) 'Abd al-Samad and Surayj narrated to us, they said: Mulazim ibn 'Amr narrated to us, 'Abd Allah ibn Badr narrated to us, that 'Abd al-Rahman ibn 'Ali narrated to him, that his father 'Ali ibn Shayban narrated to him, that he went as a delegate to the Messenger of Allah, peace and blessings be upon him. He said: We prayed behind the Prophet, peace and blessings be upon him, and he glanced with the corner of his eyes at a man who was not straightening his back in bowing and prostration. When the Messenger of Allah, peace and blessings be upon him, finished, he said: "O assembly of Muslims, there is no prayer for the one who does not straighten his back in bowing and prostration." He said: And he saw a man praying behind the row, so he waited until the man finished, then the Messenger of Allah, peace and blessings be upon him, said: "Repeat your prayer, for there is no prayer for a man who prays alone behind the row."