Charles Ellicott Commentary Galatians 4:7

"So that thou art no longer a bondservant, but a son; and if a son, then an heir through God." — Galatians 4:7 (ASV)

Thus, by your redemption, adoption, and the gift of the Spirit, it is clearly proven that the old state of servitude and minority is past. You have entered upon the full privileges of the adult son. And the son is also called to the Messianic inheritance.

Thou.—The singular is used in order to individualize the expression and bring it home pointedly to each of the readers.

No more.—Since the coming of Christ, and your own acceptance of Christianity.

If a son, then an heir . . .—The Roman law (which the Apostle seems to be following) treated all the sons as heirs, and provided for an equal division of the property between them.

Of God through Christ.—The true reading here appears to be, through God—a somewhat unusual expression. The Christian is admitted as an heir, not through any merits of his own, but through the process of redemption and adoption accomplished for him by God.