When the right time came, God sent forth His Son from Heaven in His pre-existent state, into the world. He was born of a woman (virgin birth) and was made subject to the requirements of the law. Jesus was sent at a specific time. 

Jesus entering into the physical realm was not a random thing occurring at a haphazard time. There were developments that had to take place before Christ could come to earth and redeem man. 

The Father sent His Son to the earth at the earliest possible time. Anytime before that would have been too soon.

His purpose for coming into the world was: first, He came to "redeem them that were under the law." He did this by perfectly keeping the law, fulfilling it, and paying its curse (Matthew 5:17; Galatians 3:13). Jesus delivered us from the entire system of the law. The Greek word for redeem means "to buy OUT OF the slave market." secondly, Jesu gave us sonship with all its privileges. Not only were we redeemed from the bondage of the law, but we were redeemed unto sonship. 

Many people stop short, only realizing what they were delivered from, not what they inherit. We need to rejoice that we are redeemed, but we also need to move on, and realize the full benefits of our inheritance.

God created us for Himself but we sold ourselves into slavery to the devil. God bought us back through the precious blood of Jesus Christ. No amount of effort, human works, or man's own righteousness could bring God's favor that we needed. It was the actual life of God (Leveticus 17:11) that purchased our redemption.