9 And they came to the place which God had told him of; and Abraham built an altar there, and laid the wood in order, and bound Isaac his son, and laid him on the altar upon the wood. 10 And Abraham stretched forth his hand, and took the knife to slay his son.
Evidently Abraham had concluded that if he was going to follow through with this sacrifice, then he was going to do it fully and properly. Notice that he took the time to erect an altar, lay out the wood “in order,” and lay his son upon that altar, just as he would do for any other sacrifice. This was an offering to the almighty God, and he was going to do it with the same reverence and meticulous detail that he gave to all other such sacrifices.
It also stands out to me that the famous depiction of Abraham standing over his son, knife raised toward heaven, about to plunge it down may not be accurate. That, of course, is the most dramatic way to depict things, but all the record actually says is that Abraham had picked the knife up. Perhaps he did, in fact, step to the altar and raise his hand before the angel appeared, or perhaps not. In any case, it seems to be the grabbing of the knife that was the line Abraham had to cross before God was satisfied with his commitment.