‘For he is not a Jew who is one outwardly, nor is that circumcision which is outward in the flesh, but he is a Jew who is one inwardly (hiddenly), and circumcision is that of the heart, in the spirit not in the letter, whose praise is not of men, but of God.'
Paul now concludes his argument by describing ‘the true Jew'. Based on his arguments above, being a Jew is not something dependent on a man's own outward claims or on the external evidence of circumcision. It is rather based on what he is hiddenly (there is no physical sign apart from behaviour), when he demonstrates a genuine response to God's law. Thus we learn now that the true Jew is one who is circumcised in heart, in the spirit (in genuine spiritual response or in the Holy Spirit or both) and not in the letter (not just physically circumcised because it is written down in the Law), for such a man receives praise from God rather than from men (see 2 Corinthians 5:10). The man whose heart is right with God in the Spirit is the one who pleases Him. Here we have the clear indication that the true Jew is the believer in Christ through the Spirit.
This conclusion is of immense importance. It indicates that Paul sees all true Christians as true Jews (see Philippians 3:3), and conversely that unbelieving Jews had ceased in God's eyes to be Jews because they had been ‘cut off' (Romans 11:17 onwards). It is a reminder that it is Christ's people who are now to be seen as the true Israel. Unbelieving Israel has been cut off (Romans 11:17 ff) and all true believers, whether Jew or Gentile, form the true Israel of God (Romans 11:17-28; Galatians 3:29; Galatians 6:16; Ephesians 2:11-22; 2 Peter 2:9).
So Paul has demonstrated that neither possession of the Law nor physical circumcision put a man into a position of special privilege unless they are accompanied by full obedience to the Law, something which is impossible. Instead therefore it is necessary to be circumcised in heart ‘in the Spirit' in order to be a true Jew.
‘Whose praise is not of men, but of God.' There is a play on ideas here. The word Jew, signifying initially a man of Judah, contains within it the thought of ‘praise' (see Genesis 29:35; Genesis 49:8). But Paul wants it to be clear that the only one who is a true Jew and who is really deserving of praise from God is the one who is ‘circumcised in heart', in his spirit (or ‘in the Spirit'). He alone is the one whom God will praise (2 Corinthians 5:10).