Abraham agrees to the seemingly cruel request by God that he sacrifice his one and only son because he truly fears God and holds himself to God’s mercy. If not for his earlier dedication towards God, Isaac would not have been born to him in the first place. So, since Isaac was God’s gift to Abraham, God also has the power to take Isaac away, and Abraham recognizes this. In fact, when Abraham tells Isaac that “God will provide himself the lamb for a burnt offering” (Gen 22:8), he is not lying because God did in fact provide Isaac (“the lamb”) to Abraham. Furthermore, they both end up returning to the two young men mention in 22:5, so Abraham’s promise of returning to them is not a lie either.
God does this to Abraham as a sort of test of his loyalty. He wants to see if Abraham will willingly give up Isaac, who was a gift to him. If Abraham refused to give up Isaac, then God would not be giving Isaac to him, but rather Abraham would be “taking” Isaac, similar to the way Eve “took” the forbidden fruit in the garden of Eden. In God’s eyes, Abraham is certainly praiseworthy because he does not take his own judgment over God’s and remains loyal unlike most of those that came before him. In testing Abraham God’s actions can seem praiseworthy in that he had perfect judgment towards Abraham’s loyalty, and because of this His demanding of the sacrifice can be seen the greatest test for humanity yet.
James Duke, Foundations of Theology 