It is written that Abraham had two sons: the one by a bondwoman, the other by a freewoman. --Galatians 4:22
Paul was not dealing with sin in this chapter of Galatians, but with the relation of the natural to the spiritual. The natural can be turned into the spiritual only through sacrifice. Without this a person will lead a divided life. Why did God demand that the natural must be sacrificed? God did not demand it. It is not God’s perfect will, but His permissive will. God’s perfect will was for the natural to be changed into the spiritual through obedience. Sin is what made it necessary for the natural to be sacrificed.
Abraham had to offer up Ishmael before he offered up Isaac (see Genesis 21:8-14). Some of us are trying to offer up spiritual sacrifices to God before we have sacrificed the natural. The only way we can offer a spiritual sacrifice to God is to “present [our] bodies a living sacrifice…” (Romans 12:1). Sanctification means more than being freed from sin. It means the deliberate commitment of myself to the God of my salvation, and being willing to pay whatever it may cost.
If we do not sacrifice the natural to the spiritual, the natural life will resist and defy the life of the Son of God in us and will produce continual turmoil. This is always the result of an undisciplined spiritual nature. We go wrong because we stubbornly refuse to discipline ourselves physically, morally, or mentally. We excuse ourselves by saying, “Well, I wasn’t taught to be disciplined when I was a child.” Then discipline yourself now! If you don’t, you will ruin your entire personal life for God.
God is not actively involved with our natural life as long as we continue to pamper and gratify it. But once we are willing to put it out in the desert and are determined to keep it under control, God will be with it. He will then provide wells and oases and fulfill all His promises for the natural (see Genesis 21:15-19).