“But when the fullness of the time was come, God sent forth his Son, made of a woman, made under the law.”
Christ entered into the world at the perfect time, when the fullness of time was come.
He entered as an Israelite and was born into the Old Covenant of Law.
Christ was sinless, he kept the law and fulfilled it all, on our behalf and in our place.
When he died in our place, he took all the punishment we deserved and we received all the riches and treasures of heaven that he deserved.
It was the great exchange:
His righteousness in place of our condemnation.
His sonship in place of our alienation.
His perfect health in place of our sickness.
His riches and inheritance in place of our poverty.
His new life in place of our death.
His life living inside of us in place of our separation.
We now are united with him and he lives in his fullness in us.
Andrew Wommack here explains the Father’s Plan:
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. The entrance of Jesus 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 prior to the time Jesus was born of the virgin Mary, would have been premature.
His purpose for coming into the world was twofold. 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 (Mt. ; Gal. ). Thus, Christ delivered us from the entire system of the law. The Greek word for redeem means "to buy OUT OF the slave market."
Secondly, Christ gave us the status of 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. Sure, 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 the divine favor that we needed. It was the actual life of God that purchased our redemption.