It's a test. God will not withhold his Son because Abraham did not withhold his son.
Think about what God is saying. He's really laying it on thick, 'Take now thy son, thine only son, who you love.' Wait a minute. Abraham has another son. What about Ishmael, his son with the Egyptian Hagar? Obviously there is more going on here than meets the eye.
-Isaac had to carry the wood for the sacrifice up the mount just like Jesus had to carry the cross to Cavalry.
-God tells Abraham to go to Mount Moriah. Calvary is the highest mountain in the Moriah mountain range.
-Isaac says' I see the fire and the wood but where is the lamb?' Abraham replies 'God will provide himself a lamb.' Jesus is the lamb of God, slain before the foundation of the world (Revelation 13:8), who takes away the sins of the world (John 1:29).
-Isaac is essentially raised from the dead, again a symbol of Jesus.
-Afterwards, Abraham calls the place Jehovah-jireh which means God provides. Little did Abraham and Isaac know that as they were climbing the mountain, wracked with an agony of emotions, that the ram, God's provision, is coming up the other side of the mountain. That's just like us with the problems in our own lives. When we are going through them, life's problems seem so big but unbeknownst to us God's supernatural provision is coming up the other side to meet us.
-God is pictured as the Ancient of days as he is described in Daniel chapter 7 from the Old Testament and Revelation chapter 1 in the New Testament. He is white as wool with eyes of fire and a garment white as snow. The rainbow around his head comes from the rainbow around God's throne in Revelation 4 and the rainbow around the angel of the Lord's head in Revelation 10.