The story of the nativity is written on our hearts: it was taught to most of us when we were children, and it is part of our culture. But many people who know of the nativity will not know much more about Christianity, or why the Christmas story is so important to our faith.
Christians believe that God himself came to live with us. Jesus was born of the virgin Mary and through the Holy Spirit: he was both fully human and also fully divine. His nature is the same as God the Father, so Jesus is powerful, good and is the Creator of all things, but yet he humbled himself to come and live among us and show us his love. This was predicted hundreds of years before Jesus' birth: that a virgin would have a son, and he would be called 'God with us' or 'Immanuel'.
Of course the Christian idea of the Trinity is important too. There was a relationship between God the Son while he was living on earth, and God the Father, so there are different 'persons' within the one God that Christians believe in.
The idea that there is one God who came to earth in the human form of Jesus is what makes Christianity unique, and is one of the aspects of our faith that prevents any kind of 'all religions are true' broadbrush claims. From Muslims to Jehovah's Witnesses, the belief that God himself became man is not accepted by other religions. Yet it is absolutely fundamental to Christian belief.
Here are a few of the reasons why it's important that God came to earth in the form of Jesus.
1. Jesus (and therefore, God) suffered in the same way that we suffer
God did not leave us on our own in the pain and problems of this world. Jesus was mocked, rejected, and tortured, so he understands exactly what we are going through when we are suffering. Because God came in the form of Jesus, we can never say of Him, "He just doesn't understand." In fact he chose to be born as a child of a group of people who were being oppressed and mistreated, apparently fatherless, in poverty, in the muck and cold of a stable.
2. It means that God has been tempted in exactly the same way that we have
Hebrews 4:15 says that Jesus "understands our weaknesses, for he faced all of the same testings we do, yet he did not sin" and in 2:18 it says, "Since he himself has gone through suffering and testing, he is able to help us when we are being tested." Because Jesus went through what we went through but did not sin, we can have confidence that giving our lives to Jesus will conquer the bad behaviour that shackles us.
3. Jesus coming as God means that we can understand much more clearly who God is and what He is like
God is not some invisible, impersonal force that is a mystery to us. Colossians 1:15 says: "Christ is the visible image of the invisible God." Because Jesus is God in the flesh, we can learn more vividly what makes Jesus sad, what makes him angry, how he treated people and what he taught. It's often asked, why doesn't God come down from heaven and talk to us? And the Christian answer is that he did. Jesus shows that God is personal and so we can relate to Him now, in the present, in the same way.
4. Jesus' being in the same form as us meant that he was able to take on the sins of the human race
By coming to earth as God in the flesh, he enabled our redemption through his death on the Cross. "Therefore, it was necessary for him to be made in every respect like us, his brothers and sisters, so that he could be our merciful and faithful High Priest before God. Then he could offer a sacrifice that would take away the sins of the people" (Hebrews 2:17). Jesus bore the weight of all our sin and death when he hung on the Cross. Only God could bear this weight in order to free the human race from this darkness.
5. We can receive a clear, unambiguous teaching from God himself on what is expected of us and how to find salvation
Jesus teachings are widely accepted as being wise and beautiful by most religions. But if Jesus was just a man, then they're just one among other writings that are knocking around. Instead, Christians believe that the radical message of love and sacrifice that Jesus gave was spoken by God and lived by God.
The nativity is more than just a nice children's story, it's the very foundation of the Christian faith. Jesus can show us how much God loves us, and also what God wants us to do. He can also rescue us from the consequences of failing to live as God wants us to do. God was and is with us, on earth and forever more.
