The Old Testament saints were under the guardianship of the law until Christ came, but they thought they were, of all people, most free. In reality, they were enslaved to forces they neither understood nor could control, just as were the Gentiles. Christ came to redeem those who were so enslaved, both Jew and Gentile, and he did so on God’s terms, at God’s time, and through no work or labor of our own. Because of Christ, God gives to those who trust in him the full rights and privileges of a son. As proof of this, and to accomplish his will in them, God gives to these redeemed ones the Holy Spirit, who cries out to the Father from within to testify to their relationship with God.
Since all of this was done under God’s initiative, in God’s power, through God’s means, and since you were unable to contribute in any way to this divine plan except for faith in Christ, why then would you believe that you can maintain this relationship on your own terms, through your own means, by your own labor? Such thought is foolishness. You are not a slave any longer; you are God’s son. You are his heir simply because you are his son. Live like his son, enjoy the privilege of being his son, and don’t live like you can or must work to earn his favor.
They worshipped and served other Gods because they were ignorant of the one true God. God has since revealed himself in Christ and so they can say that they now truly know God. More importantly, they are known by God, and thus have been adopted. In their return to the observance of the law with its rituals and holy days, they are really returning to the bondage under which they lived when they were ignorant of God. It is as if Paul has wasted his time and energy to bring to Christ.
Even our knowledge of God is the result of God’s initiative. While we must know him, we only know him because he knows us and has revealed himself. Those elements of the law and of nature that you worshipped and served before know God, they could not bring you close to God then, why would you believe that they can bring you closer to God now? Stop ignoring the grace of God by going back into bondage through slavishly observing human standards in a foolish attempt to determine who is closer to God and who is not.