But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God. - Romans 2:29
The spiritual lineage of the children of God is traceable only to the Lion of the tribe of Judah—the Lord Jesus Christ— God The Son. The triune love of the eternal Godhead begat the infinite desire of divine purpose. God alone is to be praised for the supernatural indwelling of the mystical person of Christ in Spirit. Circumcision of the heart, the identifying and distinguishing mark of a child of God, is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory (Col 1:27). Christ in you separates the children of God from all other people and creatures.
The difference lies in heart and in Spirit, A new heart also will I give you, and a new spirit will I put within you (Ez 36:26). The Jews boasted in the law (outwardly); the Gentiles boasted without the law (outwardly). However God’s Word declares, circumcision verily profiteth, if thou keep the law: but if thou be a breaker of the law, thy circumcision is made uncircumcision (Rom 2:25). The new heart and Spirit imparted to the children of God operates by love, produces an inward desire, spiritual obedience, faith, love, and devotion to Christ, and excludes boasting. This is not a servile obedience to the letter of the law which genders boasting. For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast (Eph 2:8).
Although one may make a fair show in the flesh, if he has not the Spirit of Christ and a heart for Christ, he cannot be truthfully called a child of God—though I bestow all my goods to feed the poor, and though I give my body to be burned, and have not charity (love for Christ), it profiteth me nothing (1 Cor 13:3). It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life (Jn 6:63).