For it is not he is a Jew, who is so outwardly; nor is that circumcision which is outwardly in the flesh:

For the true Jew is not the man who is simply a Jew outwardly, and true circumcision is not that which is outward and bodily.

The true Jew is not one who is only so publicly, and circumcision is not that which may be seen in the flesh:

For a Jew is not he who seems so outwardly. Neither is circumcision that which seems so outwardly, in the flesh.

For a man who is only a Jew outwardly is not a real Jew; nor is outward bodily circumcision real circumcision. The real Jew is the person who is a Jew in soul;

Non enim qui est in aperto Iudæus est; ne quæ in aperto est circumcisio in carne, ea est circumcisio:

For a Jew is not he, etc. The meaning is, that a real Jew is not to be ascertained, either by natural descent, or by profession, or by an external symbol; that the circumcision which constitutes a Jew, does not consist in an outward sign only, but that both are inward. And what he subjoins with regard to true circumcision, is taken from various passages of Scripture, and even from its general teaching; for the people are everywhere commanded to circumcise their hearts, and it is what the Lord promises to do. The fore-skin was cut off, not indeed as the small corruption of one part, but as that of the whole nature. Circumcision then signified the mortification of the whole flesh.

For he is not a Jew - He who is merely descended from Abraham, and is circumcised, and externally conforms to the Law only, does not possess the true character, and manifest the true spirit, contemplated by the separation of the Jewish people. Their separation required much more.
Neither is that circumcision - Neither does it meet the full design of the rite of circumcision, that it is externally performed. It contemplated much more; see Romans 2:29.

For he is not a Jew - A genuine member of the Church of God, who has only an outward profession.
Neither is that circumcision - Circumcision is a rite which represents a spiritual thing, viz. the change and purification of the heart, as may be seen, Jeremiah 4:4, Jeremiah 4:6, Jeremiah 4:10; Jeremiah 9:26; Ezekiel 44:7, Ezekiel 44:9.

For he is not a Jew, which is one (u) outwardly; neither [is that] circumcision, which is outward in the flesh:
(u) By the outward ceremony only.

For he is not a Jew which is one outwardly,.... The apostle removes the plea in favour of the Jews, taken from their name and privilege, by distinguishing between a Jew and a Jew, and between circumcision and circumcision: "he is not a Jew which is one outwardly"; by mere name, nature, nation, religion, and profession:
neither is that circumcision which is outward in the flesh; which takes away the flesh of the foreskin, but not the carnality of the heart; leaves a mark upon the flesh, but no impression on the mind. This is nothing, is not the true, solid, substantial, spiritual circumcision, which only avails in the sight of God.

he is not a Jew which is one outwardly, &c.--In other words, the name of "Jew" and the rite of "circumcision" were designed but as outward symbols of a separation from the irreligious and ungodly world unto holy devotedness in heart and life to the God of salvation. Where this is realized, the signs are full of significance; but where it is not, they are worse than useless.
Note, (1) It is a sad mark of depravity when all that is designed and fitted to melt only hardens the heart (Romans 2:4, and compare 2-Peter 3:9; Ecclesiastes 8:11). (2) Amidst all the inequalities of religious opportunity measured out to men, and the mysterious bearing of this upon their character and destiny for eternity, the same great principles of judgment, in a form suited to their respective discipline, will be applied to all, and perfect equity will be seen to reign throughout every stage of the divine administration (Romans 2:11-16). (3) "The law written on the heart" (Romans 2:14-15) --or the Ethics of Natural Theology--may be said to be the one deep foundation on which all revealed religion reposes; and see on Romans 1:19-20, where we have what we may call its other foundation--the Physics and Metaphysics of Natural Theology. The testimony of these two passages is to the theologian invaluable, while in the breast of every teachable Christian it wakens such deep echoes as are inexpressibly solemn and precious. (4) High religious professions are a fearful aggravation of the inconsistencies of such as make them (Romans 2:17-24). See 2-Samuel 12:14. (5) As no external privileges, or badge of discipleship, will shield the unholy from the wrath of God, so neither will the want of them shut out from the kingdom of heaven such as have experienced without them that change of heart which the seals of God's covenant were designed to mark. In the sight of the great Searcher of hearts, the Judge of quick and dead, the renovation of the character in heart and life is all in all. In view of this, have not all baptized, sacramented disciples of the Lord Jesus, who "profess that they know God, but in works deny Him," need to tremble--who, under the guise of friends, are "the enemies of the cross of Christ?"

For he is not a Jew - In the most important sense, that is, one of God's beloved people. Who is one in outward show only; neither is that the true, acceptable circumcision, which is apparent in the flesh.