Circumcision acts as a physical marker for the Jewish people of their covenantal identity: that they are called to be separate from those around them in obedience to God and His law. Paul here is making the case that outward, physical circumcision has no value if it is not partnered with inward obedience, or circumcision of the heart.

God calls us to inward obedience that sets us apart from those around us, more so than any physical act we might do. We are to set our hearts apart in full obedience to Him alone.