Augustine of Hippo

Now Paul says that Christ will profit them nothing if they are circumcised, that is, in the physical way that his opponents wanted, namely, to put their hope of salvation in circumcising their flesh. For Paul himself circumcised Timothy as a young man when he was already a Christian. This he did [to avoid] scandalizing his own people, not at all in dissimulation but from that indifference which made him say "circumcision is nothing, uncircumcision is nothing." For circumcision is no impediment to the one who does not believe that his salvation lies in it.