If you accept circumcision, Christ will be of no advantage to you. Galatians 5:2
“Paul does not say that works of themselves are nothing, but that confidence and righteousness in them are nothing, for that would make Christ of no value. . . .
Let us bear this in mind when the devil accuses and frightens our conscience, attempting to drive us to despair. He is the father of lying and the enemy of Christian freedom; he torments us every moment with false fears, so that when our conscience has lost this Christian freedom, it will feel remorse for sin and condemnation and always remain in anguish and terror. When that great dragon — that old snake, the devil — comes and tells you that not only have you done no good, but you have also transgressed God’s law, say to him, ‘You are troubling me with the memory of my past sins; you are also reminding me that I have done no good. But this is nothing to me, for if I either trusted in my own good deeds or feared because I have done no such deeds, Christ would in either case be of no value to me at all. I rest only in the freedom Christ has given me. I know he is of value to me, and so I will not make him of no value, which I would be doing if I either presumed to purchase favor and everlasting life for myself by my good deeds or despaired of my salvation because of my sins.’”
Martin Luther, Galatians (Wheaton, 1998), pages 245-246.