Sahih Ibn Khuzaymah

Hazrat Abbas bin Sahl al-Sa'idi narrates that some individuals from the Ansar gathered. Among them were Hazrat Sahl bin Sa'd al-Sa'idi, Abu Humayd al-Sa'idi, and Abu Usaid al-Sa'idi. They discussed the prayer of the Messenger of Allah (peace be upon him). So, Sayyiduna Abu Humayd (may Allah be pleased with him) said, "Allow me to describe (the prayer of the Messenger of Allah, peace be upon him) to you, for I know it better than you." They said, "(If that is so) then describe it." He said, "I saw the Messenger of Allah (peace be upon him) perform the best ablution, then he entered the prayer and said the takbir, raising both his hands to the level of his shoulders. Then, when he bowed (in ruku'), he placed both his hands on his knees as if he were grasping them. (In ruku') he neither raised his head nor lowered it excessively (but kept it in a moderate position, level with his back), and he kept his arms away from his sides. Then, when he raised his head (from ruku'), he stood up straight until every bone returned to its place." Then Janab Bundar narrated the rest of the hadith, and at the end of the hadith, these words were mentioned: "All the noble companions (may Allah be pleased with them) said: 'The prayer of the Messenger of Allah (peace be upon him) was like this.'" Imam Abu Bakr (may Allah have mercy on him) said: "I heard Muhammad bin Yahya saying that whoever, after hearing this hadith, does not raise his hands when going into ruku' and when rising from ruku', his prayer is incomplete."