Mus’ab b sa’d said: I prayed by the side of my father. I put both of my hands between my knees(in bowing condition). He prohibited me from it. I then repeated; so he said: Do not do so, because we used to do so. But we were prohibited to do that, and commanded to put our hands on the knees
SahihSahihSahihBook 2 · Hadith 477