Adam Clarke on 1 Corinthians 7:19

Circumcision is nothing - Circumcision itself, though commanded of God, is nothing of itself, it being only a sign of the justification which should be afterwards received by faith. At present, neither it nor its opposite either hinders or furthers the work of grace; and keeping the commandments of God, from his love shed abroad in a believing heart, is the sum and substance of religion.