Sahih Ibn Khuzaymah

It is narrated from Hazrat Muhammad bin Ata, who reports from Sayyiduna Abu Humayd Sa'idi (may Allah be pleased with him) that I heard him among ten companions, among whom was also Sayyiduna Abu Qatadah bin Rabi'i (may Allah be pleased with him). He says that when the Prophet Muhammad (peace and blessings be upon him) would stand for prayer, he would stand with moderation. And after narrating a part of the hadith, he said: Then the Prophet (peace and blessings be upon him) bent towards the ground for prostration, then said « اللهُ أَكْبَرُ », then kept both his arms away from his sides and spread the toes of his feet.

Hazrat Muhammad bin Amr bin Ata narrates that he was sitting with a group of the noble Companions when they discussed the prayer of the Messenger of Allah, peace and blessings be upon him. Then Sayyiduna Abu Humaid Sa’idi, may Allah be pleased with him, said: I remember the prayer of the Messenger of Allah, peace and blessings be upon him, better than all of you. (I saw the Messenger of Allah, peace and blessings be upon him, that when he said « اللهُ أَكْبَرُ » to begin the prayer, he raised both his hands up to the level of his shoulders. Then when he bowed for ruku’, he firmly placed both his hands on his knees. Then he bent his back. Then when he raised his blessed head, he stood up completely straight until every bone of his returned to its place. And when he performed sajdah, he neither spread his hands too wide nor kept them completely close, and he directed the toes of both his feet towards the qiblah.)