‘And the angel of Yahweh called to him from Heaven and said, “Abraham, Abraham.” And he said, “Here I am.” And he said, “Do not lay your hand on the lad, neither do anything to him, for now I know that you fear God, seeing the you have not withheld your son, your only son from me.” '
At last the change to the name Yahweh. The covenant has not been forgotten. The angel of Yahweh is clearly God Himself for He says, “you have not withheld your only son ‘from Me'.”
“Now I know that you fear God.” ‘I know' - an anthropomorphism. It was not that God needed to be convinced of Abraham's faithfulness. He is the One Who knows the heart. It was rather that Abraham might be reassured, and that the world might later know, that Abraham would hold nothing back from God whatever the cost. This act has brought out Abraham's total obedience and submission. He had passed the ultimate test.
To ‘fear God' means to have such a reverence and awe for Him that we obey Him. It is strongly linked to the idea of obedience (compare 20:11; 42:18; 2 Kings 4:1; Job 1:1; Job 1:8; Proverbs 1:7; Isaiah 11:2). Thus God wants Abraham to know that He fully appreciates what he has been willing to do.