It was narrated that Mus’ab bin Sa’d said: “I bowed (in prayer) beside my father, and I put my hands between my knees. He struck my hand and said: ‘We used to do that, then we were commanded to put them on the knees.’”
It was narrated that ‘Aishah said: “The Messenger of Allah (ﷺ) used to bow with his hands on his knees and his upper arms held away from his sides.”