The Heidelberg Catechism

Question 16. Why must our mediator and deliverer be a true man, and also perfectly righteous?

Answer: He must be a true man because the justice of God requires that the same human nature which has sinned should pay for sin; (a) and he must be perfectly righteous because one who is himself a sinner cannot pay for others. (b)

(Click through to see scriptural proofs.)

a. Romans 5:12, 15, 18

Therefore, just as sin came into the world through one man, and udeath through sin, and vso death spread to all men because all sinned … 

But the free gift is not like the trespass. For if many died through one man’s trespass, much more have the grace of God and the free gift by the grace of that one man Jesus Christ abounded for many.

Therefore, as one trespass led to condemnation for all men, so one act of righteousness leads to justification and life for all men.

      1 Corinthians 15:21

For as by a man came death, by a man has come also the resurrection of the dead.

      Hebrews 2:14-16

Since therefore the children share in flesh and blood, he himself likewise partook of the same things, that through death he might destroy the one who has the power of death, that is, the devil, and deliver all those who through fear of death were subject to lifelong slavery. For surely it is not angels that he helps, but he helps the offspring of Abraham.

      Isaiah 53:4-5, 10-11

Surely he has borne our griefs

and carried our sorrows;

yet we esteemed him stricken,

smitten by God, and afflicted.

But he was pierced for our transgressions;

he was crushed for our iniquities;

upon him was the chastisement that brought us peace,

and with his wounds we are healed.

Yet it was the will of the Lord to crush him;

he has put him to grief;

when his soul makes an offering for guilt,

he shall see his offspring; he shall prolong his days;

the will of the Lord shall prosper in his hand.

Out of the anguish of his soul he shall see and be satisfied;

by his knowledge shall the righteous one, my servant,

make many to be accounted righteous,

and he shall bear their iniquities.

b. Hebrews 7:26-27

For it was indeed fitting that we should have such a high priest, holy, innocent, unstained, separated from sinners, and exalted above the heavens. He has no need, like those high priests, to offer sacrifices daily, first for his own sins and then for those of the people, since he did this once for all when he offered up himself.

      1 Peter 3:18

For Christ also suffered once for sins, the righteous for the unrighteous, that he might bring us to God, being put to death in the flesh but made alive in the spirit … .