WHY must Jesus be God AND man?

I hear a lot of people who are not believers say that they believe that Jesus was a man. They say, "He was a good man, but just that a man."

If we think of Jesus as only a man, we can't have hope. Yes, Jesus did come to live on the earth. He was born of a woman, and raised like many other children. However, if He was only a man, we would not have salvation. Jesus would not have lived a sinless life. He could not have raised himself from the dead.

1 Corinthians 15:14 says, "And if Christ has not been raised, our preaching is useless and so is your faith." Furthermore, verse 17 in that same passage states, "And if Christ has not been raised, your faith is futile; you are still in your sins."

As man, Jesus represents us on the cross. As God, He redeems us on the cross.
— Matthew Spandler-Davison

We can't have forgiveness of our sins if Jesus was only a man. Our lives are pointless. However, God saw our need for a Savior, and He sent Jesus His son. Going a few more verses in 1 Corinthians 15:20-22, we see that because sin entered the world through Adam, a man, Jesus, brought resurrection to us.

I've never given much thought to Jesus as only God, and I think that I can't think of Jesus as God only because in Jesus becoming a man, I can relate to Him. He went through trials and temptations, just like me. If He had stayed only as God, who could I look to as my perfect example? We know that Jesus is God though because He says in John 10:38, "But if I do them, even though you do not believe me, believe the works, that you may know and understand that the Father is in me, and I in the Father."

Jesus has to be both, man and God.  

Jesus had to become man in order to take our sin and punishment onto Himself, but He had to be God to be raised and defeat the chains of death. We now have salvation and purpose through the life, death, and resurrection of Jesus Christ, as fully God and fully man.