“…to redeem those who were under the law, that we might receive the adoption as sons”
There are two reasons Jesus came:
1) to redeem those under the law, and
2) to fix the full rights of privilege with God for the believer.
to redeem those who were under the law,
Everyone falls under the judgment of the law. That is why Jesus came “to redeem” those under the law. The word “redeem” means to buy back, to pay full. Jesus purchased us out of the slave market of sin. He fully paid the price sin incurred through the penalty of the law. We were in bondage to sin, but Jesus delivered us from sin by paying the price for sin (3:13). Jesus redeemed us from the entire Mosaic system of life, from bondage to the ceremonial law.
Jesus paid the full price for the penalty of our sin.
If the law bosses us around, we are under the authority of the law. Christ freed us from the law as a rule of life by His death on the cross. If we revert to the law, we revert to childhood spiritually.
Jesus paid the full price for the penalty of our sin. We incur no debt with God. Jesus left no bill unpaid. He paid the price once for all. He killed hell eternally for the believer. The Son of God became the Son of Man that the sons of men might become the sons of God. That is what it cost the Son of God to make me a son of God.