Bayhaqi 2532 — Those who mentioned raising the hands only

It is narrated from Alqamah that Sayyiduna Abdullah (bin Mas'ud, may Allah be pleased with him) said: "The Messenger of Allah (peace and blessings be upon him) taught us the prayer. He said the takbir and raised his hands. Then, when he bowed, he joined both his hands together and let them hang between his knees." Alqamah says: When this reached Sayyiduna Sa'd (may Allah be pleased with him), he said: "My brother has spoken the truth. Formerly we too used to do it this way; then we were commanded to place the hands on the knees (that is, to grip them firmly from above)."
The Shaykh says: If the hadith is as Abdullah bin Idris (may Allah have mercy on him) narrated it, then it does not mention raising the hands again; and if it is as al-Thawri (may Allah have mercy on him) narrated it, then the hadith of Ibn Idris (may Allah have mercy on him) shows that this practice belonged to the early period of Islam, just as letting the hands hang between the knees belonged to the early period of Islam. Then after that the practices were laid down and the Shari'ah advanced in stages (that is, rulings changed gradually). Those who were to memorise them memorised them and passed them on, and now acting upon them has become obligatory.