John Calvin Commentary Galatians 6:15

"For neither is circumcision anything, nor uncircumcision, but a new creature." — Galatians 6:15 (ASV)

For in Christ Jesus. The reason why he is crucified to the world, and the world to him, is that in Christ, to whom he is spiritually united, nothing but a new creature is of any avail. Everything else must be dismissed, must perish. I refer to those things which hinder the renewing of the Spirit.

If any man be in Christ, he says, let him be a new creature. (2 Corinthians 5:17). That is, if any man wishes to be considered as belonging to the kingdom of Christ, let him be created anew by the Spirit of God; let him not live any longer to himself or to the world, but let him be raised up to newness of life. (Romans 6:4). His reasons for concluding that neither circumcision nor uncircumcision is of any importance have already been considered. The truth of the gospel swallows up, and brings to nothing, all the shadows of the law.