Upvote:2
I don't think the interpretation is to show that, "God's foreknowledge is justified." The following is from John Gill who is quoting someone else.
Psalm 1:6; Saadiah Gaon (i) interprets it, "I have made known", that is, to others; God by trying Abraham made it manifest to others, to all the world, to all that should hear of or read this account of things, that he was a man that feared God, loved him, believed in him, and obeyed him, of which this instance is a full and convincing proof:"
Or to put it another way, "The sacrifice was already accomplished in Abraham's heart." As I'm typing this I thought of what Jesus said at John 21:15-17. He ask Peter if he loved Him three times. Do you think that Jesus knew this already?