Circumcision was an issue that was dividing the Hebrew and Gentile Christians. Hebrews were required to be circumcised by the law. Gentiles were not under the law and therefore not following this. However, some of the Hebrew followers of Jesus began to expect Gentile followers of Jesus to follow the law about circumcision. Paul disagreed with this quite vocally.
Paul preached the foundational doctrine of Jesus' teaching that sinners are justified by faith alone and no one is under the law.
Romans 7:4 and 6:7 backs this up that we died to the law through the sacrifice of Jesus on the cross. We died to sin through Jesus' sacrifice when we place our faith in him for our salvation. We don't need to follow rules or laws to follow Jesus.
Christians are free of the Mosaic law.
Why would we want to place ourselves back under sin? Jesus is not the minister of sin. He died as a ransom sacrifice or sin offering for all of us and rose from the dead three days later and ascended to heaven to be with his Father God. Titus 2:14 says,
who gave himself for us to redeem us from all wickedness and to purify for himself a people that are his very own, eager to do what is good.