Heidelberg Catechism, Lord’s Day 6
Q16. Why must the mediator be a true and righteous human?
A16. God’s justice demands
that human nature, which has sinned,
must pay for sin;
but a sinful human could never pay for others.
Q17. Why must the mediator also be true God?
A17. So that the mediator,
by the power of his divinity,
might bear the weight of God’s wrath in his humanity
and earn for us
and restore to us
righteousness and life.
Q18. Then who is this mediator—
true God and at the same time
a true and righteous human?
A18. Our Lord Jesus Christ,
who was given to us
to completely deliver us
and make us right with God.
Q19. How do you come to know this?
A19. The holy gospel tells me.
God began to reveal the gospel already in Paradise;
later God proclaimed it
by the holy patriarchs and prophets
and foreshadowed it
by the sacrifices and other ceremonies of the law;
and finally God fulfilled it
through his own beloved Son.