Galatians 5:11

But I, brethren, if I still preach circumcision, why am I still persecuted? then hath the stumbling, block of the cross been done away.

If I still preach circumcision ... This evidently refers to the allegations of the false teachers to the effect that Paul himself taught circumcision, an argument they reinforced, no doubt, by appealing to the known instance of Paul's circumcising Timothy, whose mother was a Jewess (Acts 16:3). Paul's reason for doing that, however, had nothing whatever to do with Timothy's salvation, but was for the purpose of avoiding and frustrating Jewish persecution. Any allegation that Paul considered circumcision as related in any manner to salvation was effectively denied by the fact that "if Paul indeed honored circumcision in any such way, the Jews would have stopped persecuting him."

The stumbling-block of the cross ... The cross of Christ was preeminently above everything else the center and citadel of Christian hope; and if Paul trusted circumcision for anything, reliance upon the Great Atonement would have been forfeited. But is is not forfeited. The cross remains!