Question: God is just and requires that we either keep the law with a perfect love of God and neighbor or be eternally punished. However, we have been so corrupted by the fall of Adam that by nature we hate God and our neighbor and daily increase our guilt. Therefore, unless we want to be lost for eternity, we must look for a Surety who completely satisfies the just judgment of God for us. But where shall we find such a Mediator and Surety?
(Note: in law, “surety” refers to someone who agrees to be legally responsible if another person fails to pay a debt or perform a duty.)
Answer: If we look around the entire world, we shall not find a single creature (a mere creature, that is) that can make satisfaction for us. For if we should look for a surety among the angels, we would immediately encounter two problems:
First, since the angels are neither guilty nor obligated to suffer on humanity’s account, the justice of God does not demand of them that they should pay what humanity owes. It would also be unfair if other creatures should be punished for something of which humanity is guilty.
Second, since our surety and mediator had to bear and overcome the infinite, eternal wrath of God, there is no doubt that an angel would have been too weak for that. An angel would have collapsed and fallen under the weight just like the demons (who were angels of light), for whom the wrath of God is so severe that they cannot overcome it but must remain beneath it, eternally damned. If, then, the angels of God are too weak to bear and overcome the heavy weight of God’s wrath for the human race, certainly no other creature (mere creatures, that is) are going to be found who can bear the weight of our sin and release us from it. (emphasis in original)
Caspar Olevianus, A Firm Foundation, p. 3