18. Circumcised, etc. As he had made mention of the calling, he takes occasion, from a particular instance, to make a digression for a little into a general exhortation, as he is wont to do in many instances; and, at the same time, he confirms, by different examples, what he had said respecting marriage. The sum is this, that in external things you must not rashly abandon the calling on which you have once entered by the will of God. And he begins with circumcisions, respecting which many at that time disputed. Now, he says that with God it makes no difference whether you are a Gentile or a Jew. Hence he exhorts every one to be contented with his condition. It must always be kept in view, that he treats only of lawful modes of life, which have God as their approver and author.