4:5

release by purchase: Jesus released by purchase those under law, that is, believing Jews. Paul goes on to say “so that we” (apparently referring to all Galatians who have become Christians, both Jews and Gentiles) can “receive the adoption as sons.” The Greek word e·xa·go·raʹzo, here rendered “release by purchase,” is also used at Ga 3:13, where Paul says: “Christ purchased us, releasing us from the curse of the Law by becoming a curse instead of us.”​—See study note on Ga 3:13.

the adoption as sons: In the Christian Greek Scriptures, Paul mentions adoption several times with regard to the new status of those called and chosen by God. Such ones are given the prospect of immortal life in heaven. As descendants of imperfect Adam, they were in slavery to sin and therefore were not born as sons of God. Because of Jesus’ sin-atoning sacrifice, they can receive adoption as sons and become “joint heirs with Christ.” (Ro 8:14-17) They themselves do not choose to be adopted as his sons. Rather, God chooses them, according to his will. (Eph 1:5) God acknowledges them as his children, or sons, from the time that he begets them by his spirit. (Joh 1:12, 13; 1Jo 3:1) But they must continue faithful until the end of their life as humans in order to receive the full realization of being adopted as spirit sons of God. (Ro 8:17; Re 21:7) That is why Paul says: “We are earnestly waiting for adoption as sons, the release from our bodies by ransom.” (Ro 8:23; see study note on Ro 8:15.) The concept of adoption was widely known in ancient times. In the Greco-Roman world, adoption was primarily intended for the benefit of the adopter, not of the one being adopted. However, Paul emphasizes that Jehovah has lovingly taken steps for the benefit of those being adopted.​—Ga 4:3, 4.