Q.17 Why must he also be true God?
A.  So that by the power of his divinity, he might bear the weight of God’s anger and in his humanity earn for us and restore to us righteouness and life.

Isa. 53; John 3:16; 2Cor. 5:21

Q.  18  And who is this mediator–true God and at the same time truly human and truly righteous?
A.  Our Lord Jesus Christ, who was given to us to set us completely free and to make us right with God.

Matt. 1:21-23; Luke 2:11; 1Tim. 2:5; 1Cor.1:30