Now why does Jeremiah mention circumcision at all? The case is, I think, parallel to his mention of another external distinction of the popular religion, the Ark of the Covenant (iii. 15). Just as in that place God promises _shepherds according to Mine heart which shall shepherd_ the restored Israel _with knowledge and prudence_, and then directly adds that, in the light and truth of those days, the ark will be forgotten (iii. 15, 16); so here, he bids the ruling classes, the actual shepherds of the nation, not to trust in their own wisdom or valour or wealth (cf. xvii. 5 _sqq._), but in _being prudent and knowing Iahvah_, and then adds that the outward sign of circumcision, upon which the people prided themselves as the mark of their dedication to Iahvah, was in itself of no value, apart from a "circumcised heart," _i.e._, a heart purified of selfish aims and devoted to the will and glory of God (iv. 4). So far as Iahvah is concerned, all Judah's heathen neighbours are uncircumcised, in spite of their observance of the outward rite. The Jews themselves would hardly admit the validity of heathen circumcision, because the manner of it was different, just as at this day the Muhammadan method differs from the Jewish. But Jeremiah puts "all the house of Israel," who were circumcised in the orthodox manner, on a level with the imperfectly circumcised heathen peoples around them. All alike are uncircumcised before God; those who have the orthodox rite, and those who have but an inferior semblance of it; and all alike will in the day of judgment be visited for their sins (cf. Amos i.).
With the increasing carelessness of moral obligations, an increasing importance would be attached to the observance of such a rite as circumcision, which was popularly supposed to devote a man to Iahvah in such sense that the tie was indissoluble. Jeremiah says plainly that this is a mistaken view. The outward sign must have an inward and spiritual grace corresponding thereto; else the Judeans are no better than those whose circumcision they despise as defective. His meaning is that of the Apostle, "Circumcision verily profiteth, _if thou keep the law_; but if thou be a breaker of law, thy circumcision hath become uncircumcision" (Rom. ii. 25). "Circumcision is nothing, and uncircumcision is nothing, _but the keeping of the commandments of God," scil._ is everything (1 Cor. vii. 19). It is "faith working by love," it is the "new creature" that is essential in spiritual religion (Gal. v. 6, vi. 15).
_Hæc dicit Dominus: Non glorietur sapiens in sapientia sua._ Glancing back over the whole passage, we discern an inward relation between these verses and the preceding discourse. It is not the outward props of state-craft, and strong battalions, and inexhaustible wealth, that really and permanently uphold a nation; not these, but the knowledge of Iahvah, a just insight into the true nature of God, and a national life regulated in all its departments by that insight. At the outset of this third section of his discourse (ix. 3-6), Jeremiah declared that corrupt Israel _knew not_ and _refused to know_ its God. At the beginning of the entire piece (vii. 3 _sq._), he urged his countrymen to _amend their ways and their doings_, and not go on trusting in _lying words_ and doing the opposite of _lovingkindness and justice and righteousness_, which alone are pleasing to Iahvah (Mic. vi. 8), Who _delighteth in lovingkindness and not sacrifice, and in the knowledge of God more than in burnt-offerings_ (Hos. vi. 6). And just as in the opening section the sacrificial worship was disparaged, taken as an "opus operatum," so here at the close circumcision is declared to have no independent value as a means of securing Divine favour (ix. 25). Thus the entire discourse is rounded off by the return of the end to the beginning; and the main thought of the whole, which Jeremiah has developed and enforced with so much variety of feeling and oratorical and poetical ornament, is the eternally true thought that a service of God which is purely external is no service at all, and that rites without a loving obedience are an insult to the Majesty of Heaven.