This is an important question, because our salvation depends on it. Christ’s work of salvation requires his two-fold nature: God and man in one perfect, glorious Person. The incarnation makes salvation possible. But how? To answer this question we need to look at the offices of Christ. According to Scripture Jesus fulfils three offices: Prophet, Priest and King. Let’s look at each of these briefly.
As our Prophet Jesus reveals God and his will to us. Long ago, according to Hebrews 1:1-4, God spoke to us by the prophets, but now God has spoken to us by his Son. Jesus is the supreme prophet that God promised in Deut. 18:15-18: “The LORD your God will raise up for you a prophet like me from among you, from your brothers - it is to him you shall listen.”
What makes Jesus the supreme prophet isn’t simply his message, but his person. Unlike the other prophets who spoke for God, Jesus is God. This means that in his preaching and in his person, he reveals God to us.
In Isaiah 9:6 God promised us a ruler. The promise makes it clear that he would establish a conquering, peaceful, eternal, messianic, righteous reign. In order to be that promised king, Jesus had to be born in the line of David. In 2 Samuel 7:16 God promised: “And your house and your kingdom shall be made sure forever before me. Your throne shall be established forever.”
Jesus is that promised ruler. He has been given “as head over all things to the church” (Eph. 1:22). Unlike the kings who came before him, Jesus has the power and the character to establish this glorious kingdom, because he is God.
Hebrews 4:14-5:10 details how a priest was chosen from among the people so that he could be a sympathetic mediator. Jesus became a man so that he could bring the sacrifice and intercede for us before the Father’s throne.
While it is true that Jesus wasn’t born in the tribe of Levi or to the house of Aaron, he was ordained as a priest after the order of Melchizedek (Psalm 110:4). This means that his priesthood is superior to Aaron’s. Jesus is a sinless High Priest and offered one all-sufficient sacrifice, because he is both God and man.
Why did Jesus have to become a man? Because our salvation would not have been possible without it.
Because of Christ,