Or, “adoption as sons.” The Jews ceased to be immature children when they, by faith, accepted Jesus as the promised Messiah (see on John 1:12, 13). Faith in Him released them from dependence on the types of the ceremonial system and gave them full rights as heirs to the promised inheritance (Gal. 4:1-3; cf. ch. 3:6-9, 14, 16, 24). Prior to the coming of faith (see on vs. 23-25) the Jews were potential but not actual heirs.
We.
Paul here speaks again as a Jew (see on v. 3). The Gentile believers had never been “under the law” in the sense here intended.
Under the law.
Literally, “under law” (see on Rom. 2:12; Gal. 2:16). That Paul does not have in mind being under the condemnation of the moral law is evident from ch. 4:21. No one would ever “desire” to be under the condemnation of the Decalogue. Reference can be only to the jurisdiction of the Jewish legal system (see on Rom. 6:14).
To redeem.
Literally, “to buy up.” The immediate context suggests that Paul is thinking particularly of buying out from “bondage,” or slavery, those who were under “tutors and governors” (see on vs. 2, 3). Along with the more important work of redeeming men from sin, Christ’s fulfillment of the types of the ceremonial system also released the Jews from further obligation to that system and from “the curse” that came upon all who ever sought salvation through compliance with its requirements (see on ch. 3:10, 13).