Why did Jesus leave His home in heaven and come to earth?
Luke 19:10 gives us the answer when Jesus said;
"For the son of man came to seek and save that which is lost."
We are lost and in sin because in the eyes of God we have all sinned and fall short of the glory of God. Man by nature is sinful; as is evidenced from the time of Adam and Eve when they disobeyed God and ate from the tree of the knowledge of good and evil. This God proclaims in Genesis 3:22;
"The man has now become like one of us, knowing good and evil."
In other words since we now know the difference in right and wrong we become responsible for our own actions and with the loss of innocence we now must decide on our salvation.
Jesus is God who has come to earth born of woman and is the perfect man and role model for us as Christians. He is with out sin and is therefore able to act as a sacrifice and die for our sin.
Hear it from John, who was there, he walked and talked with Jesus as his disciple:
"5. This is the message we have heard from Him and declare to you; God is light and in Him there is no darkness at all. 6. If we claim to have fellowship with him and yet walk in darkness, we lie and do not live by the truth.7. But if we walk in the light, as He is in the light, we have fellowship with one another, and the blood of Jesus, His Son, purifies us from all sin." 1 John 1:5-7
In verse 9 John says, "If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness."