The first reason given by the Catechism that God becomes man is in order to save us by reconciling us with God, who “loved us and sent his Son to be the expiation for our sins.” (CCC457). Jesus is able to save us because he becomes one of us, representing humanity to the Father and bringing home those who choose to unite themselves to him by faith. The incarnation of Christ is critical to understanding the atoning work he does on our behalf as one of us, and our ultimate salvation.
Unfortunately we see in some circles today the failure to understand the great mystery of Christ truly becoming one of us, a true son of Adam who comes to undo the work of the first Adam. We see this in a tendency to deny that Jesus receives his human nature from Mary. For example:
So He spoke the Word to Mary by the Message of an angel, she received It by faith. She did not have a sexual affair with God; this would be impossible because God is a Spirit. Mary was just an incubator. All she supplied was a virgin womb. God was both Father AND Mother of Jesus, Who was the Word, NOT Mary’s ovum made flesh.
I don’t know of any Christian who believes that Mary had a sexual affair with God, but not only Catholics but most of mainline Christianity would never consider Mary as “just an incubator” or believe that Christ did not receive his flesh from her ovum. And the idea that God is both father and mother of Jesus? That is flatly denied by Scripture. Jesus only refers to God as Father, never mother. And Scripture refers to Mary as the mother of Jesus at least 25 times.
Here is a another example:
Jesus is called the “second man” (1 Cor:15:47)and the “last Adam” (v. 45). Just as Adam needed no mother to contribute “half of the genes,” neither did Christ. The “first man” was created by God without father or mother. It is therefore proper to conclude that, although Mary’s womb and blood contributed to the nourishment and growth of the One to whom she gave birth, she had nothing to do with the physical origin of the body of this “second man.” He was created in her womb, just as God created Adam.
This would lend itself to a question – if God’s intent was that Christ not truly be a son of Adam but a new creation, why create him as a child in the womb at all? Why not just a fully grown man – a new Adam?
Mark Shea identifies the major problem with this approach:
In the effort to save Jesus from contact with the “degenerate” flesh of Mary, He is even saved from contact with the flesh of Adam. The problem is, that means Jesus no longer shares our human nature, but is instead the sole member of a brand new species, born of an egg created ex nihilo and implanted by divine in vitro fertilization into the animal or Incubator Unit….And that means He can’t save us from the death that Adam brought into the world, since Jesus is not a member of the human race capable of undoing what Adam did.
Christian theology over the centuries has stood firm in the understanding that our redemption by Christ occurs because he is truly one of us. Not someone who simply looks like us, but a member of the human race who can represent humanity before God and reconcile us with Him. How can someone who is not one of us reconcile us to God at all? And we can easily turn to Scripture to support this view.
In Genesis 3:15, after the fall of Adam and Eve, we see the first promise of God for a Savior who shall be from the “seed” of the woman – “I will put enmity between you and the woman, and between your seed and her seed; he shall bruise your head, and you shall bruise his heel.” And in Luke 3:38 Christ is referred to as “the son of Adam.”
Throughout Scripture the most common reference to the genealogy of Christ is his ancestry in the line of King David. Paul tells us in Romans 1:3 that Christ “was descended from David according to the flesh,” and in Romans 9:4-5 in speaking of the Jewish people he says “They are Israelites, and to them belong the sonship, the glory, the covenants, the giving of the law, the worship, and the promises; to them belong the patriarchs, and of their race, according to the flesh, is the Christ, who is God over all, blessed for ever. Amen.”
There are many other references in Scripture we can turn to as well:
Matthew 1:1 “The book of the genealogy of Jesus Christ, the son of David, the son of Abraham.”
Luke 1:31-32 “And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus. He will be great, and will be called the Son of the Most High; and the Lord God will give to him the throne of his father David.”
Luke 1:69 “and has raised up a horn of salvation for us in the house of his servant David.”
2 Timothy 2:8 “Remember Jesus Christ, risen from the dead, descended from David, as preached in my gospel”
Revelation 5:5 “Then one of the elders said to me, ‘Weep not; lo, the Lion of the tribe of Judah, the Root of David, has conquered, so that he can open the scroll and its seven seals.'”
Revelation 22:16 “It is I, Jesus, who sent my angel to you with this testimony for the churches. I am the root and the descendant of David, the bright morning star.”
From Scripture it is clear that the human nature of Christ is from the “seed” of the woman and he is a descendant of King David “according to the flesh.” He is able to redeem us by his holy cross because he is truly one of us.