And Abu Humayd (may Allah be pleased with him) said that when the Prophet (peace and blessings of Allah be upon him) raised his head from (ruku‘), he stood straight in such a way that every joint of the back returned to its place.

Narrated Thabit: Anas used to demonstrate to us the prayer of the Prophet and while demonstrating, he used to raise his head from bowing and stand so long that we would say that he had forgotten (the prostration).