Sahih Muslim · Hadith 1224
The Book of Mosques and Places of Prayer - كتاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلاَةِ
حدثنا أبو بكر بن أبي شيبة، حدثنا وكيع، عن إسماعيل بن أبي خالد، عن الزبير بن عدي، عن مصعب بن سعد، قال ركعت فقلت بيدى هكذا - يعني طبق بهما ووضعهما بين فخذيه - فقال أبي قد كنا نفعل هذا ثم أمرنا بالركب .
Ibn Sa'd reported: I bowed and my hands were in this state, i. e. they were put together, palm to palm, and were placed between his thighs. My father said: We used to do like this but were later on commanded to place them on the knees.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).