In the New Testament Galatians 5:1-12 greatly denounces Christians undergoing circumcision to become Jews. Galatians 5:1-2 for example urges Christians not to submit themselves again to a yoke of slavery as the scripture declares that anyone that submits to be circumcised makes Christ worthless to the circumcised individual. What the scripture is thus saying is that by Christ working in a believer’s life that is uncircumcised that the individual need not be circumcised but instead should be free from the Law of Moses. Thus 1 Corinthians 7:18 the scripture teaches that if a person is uncircumcised when they are called that they should not become circumcised, and this is in sharp contrast to Genesis 17:14 that reads, “Any uncircumcised male, who has not been circumcised in the flesh, will be cut off from his people; he has broken my covenant.” (KJV)
Galatians 5:3 makes the case even more powerful by saying that every man that lets himself be circumcised is obligated to obey the entire law of Moses, and in Galatians 5:4 what is taught is that those that try to justify themselves by the law are in fact alienated by Christ and have actually fallen away from grace. This is for example one reason why Christians will have completely different holidays from Jews because Christians often want to make a clear distinction between those that have submitted themselves to obeying the entire law in rejection of Christ’s grace given to the gentiles. Overall, the scripture thus demonstrates in Galatians 5:5-6 that neither un-circumcision nor circumcision have any value to Christ but that instead the only thing that counts is faith that is expressed through love because through the Holy Ghost the believers eagerly await by faith the righteousness that is hoped for.
Galatians 5:7-12 speaks very harshly toward anyone that keeps the believer from, “obeying the truth” as it describes such persuasion as being not from the one that calls the believer, and the scripture warns that the person that throws the believers into confusion will have to pay for it. Galatians 5:11 even goes so far as to show how the offence of the cross can be understood to be active because the author of Galatians was being persecuted for not preaching circumcision. What is worse is that the scripture finishes the passage by wishing that agitators that support circumcision of the Christians would as much as cut their entire penises off by going the whole way instead of just simply cutting off the foreskin.
One should however note that 1 John 3:3-6 teaches that those that have hope in Christ purify themselves, and it also teaches that everyone that sins breaks the law as sin is lawlessness. Scripture continues by showing that Christ appeared to take away sin but that no one that lives in him keeps on sinning just as no one that continues to sin has ever known or seen him. In contrast Romans 3:21-23 teaches that the righteousness of God has been made known apart from the Law as the Law and the Prophets testified to it. This righteousness is understood by the passage to come through faith in Christ Jesus to all that believe regardless of being a Gentile or a Jew because all had sinned and fallen short of God’s glory.
The point is that a person could benefit from doing the good works of the law without being circumcised as a formal commitment to obey the Law of Moses. In fact this is what Jesus means in Matthew 13:52 when he promotes teachers of the law that have become disciples of the kingdom as being like an owner of a house that brings out both new and old treasures from their storehouses. When a Christian however willingly becomes circumcised, then they become a Jew as a rejection of their Christian call as a gentile. Overall, one can however see that scripture does not condemn having infants circumcised under the Law of Moses because they do not have a choice in the matter, but adults do have a choice and that choice can clearly become a rejection of Christ.