The Heidelberg Catechism - Lord's Day 5

12. Q .  According to God’s righteous judgment we deserve punishment both  now and in eternity: how then can we escape this punishment and return to God’s favor?

    A. God requires that his justice be satisfied. Therefore the claims of this justice must be paid in full, either by ourselves or by another.

13. Q .  Can we make this payment ourselves?

     A.  Certainly not. Actually, we increase our debt every day.

14. Q . Can another creature—any at all— pay this debt for us?

      A. No. To begin with, God will not punish any other creature for  that a human is guilty of. Furthermore, no mere creature can bear the weight of God’s eternal wrath against sin and deliver others from it.

15. Q . What kind of mediator and deliverer should we look for then?

      A. One who is a true and righteous human, yet more powerful than all creatures, that is, one who is also true God.