A.T. Robertson Commentary Romans 2:25

"For circumcision indeed profiteth, if thou be a doer of the law: but if thou be a transgressor of the law, thy circumcision is become uncircumcision." — Romans 2:25 (ASV)

If thou be a doer of the law (εαν νομον πρασσεις). Condition of third class and the present (continued action) subjunctive of πρασσω, a verb meaning to do as a habit.

Is become uncircumcision (ακροβυστια γεγονεν). The Jew is then like the Gentile, with no privilege at all. Circumcision was simply the seal of the covenant relation of Israel with God.