The choice of the wording in the Quran is crucial. No word was chosen by accident or out of control. Every word and expression was deliberately chosen by God. Islam never advocated human sacrifice. God would not contradict Himself an order Abraham to commit what he prohibited even as a test.
Prophets are human beings also and as much susceptible to the tricks of Satan as everyone else.
God never left this issue unsolved. But God nullifies what the devil has done, and God perfects His revelation. God is, Omniscient, Most Wise. Because Abraham thought the dream was from God and he proceeded to sacrifice his son Ismail, God sent him the lamb to be sacrificed instead, and to save the son, and the father-son sacred relationship. No where in the Quran does God say that it was God who told Abraham to sacrifice his son.