And that place is not as the basis of justification. But as the sign and seal of the righteousness that comes by faith alone. When your life begins to conform to the will of God, this is a sign. It is a sign and seal that your faith is real and that you have an unshakable righteousness, namely, the righteousness of God in Christ. An act like circumcision, or any other act in obedience to God, does not give you your right standing with God.
Faith alone does.
But the acts of obedience are a sign and a seal that your faith is real and that Christ is your perfect righteousness. First he cancels the sin. Then he breaks the power of the canceled sin. Then, on the basis of that, sanctification. Paul wants to make this plain for us.