The Galatians accepted the first part but corrupted the second part which is why they were in danger of turning back to the elemental principles of this world (Gal. 4:3,9). The gospel of God is the good news of the kingdom of God (Mark 1:14-15). The big gospel is that Christ invaded this world to rescue us from this world!
Christ's gift not only bought us forgiveness of our sins. His gift had a higher purpose. The higher purpose is the greatest good news. Christ gave Himself "so that" (ὅπως) "He might rescue" (ἐξέληται) us. The conjunction combined with the subjunctive form of the verb is a purpose clause. The purpose proclaims the good news. Without the purpose, the good news is not so good! Forgiveness of sins without deliverance from evil is a limited and ultimately unsatisfying gospel.
The verb translated "rescue" (ἐξέληται) was used in the active voice for tearing an eye from its socket. Here the verb is in the middle voice and means to set free, deliver or rescue (BDAG, 271-272). The militaristic, even violent, overtones remain part of the imagery. This verse is the only time that Paul uses the term, preferring words like save, set free or redeem to depict our salvation. However, the verb is common in the Old Testament LXX, and we find the word frequently in Acts where it is used of the rescue of Joseph from his afflictions (7:10); the deliverance of Israel from Egypt (7:34); and God's rescue of Peter from Herod's prison (12:11) among other places (Bruce, Galatians, 75). Paul may have been unconsciously quoting from early church confessional statements here since the expressions "gave Himself for our sins" and "this present age" are used in the early church confessionals (Longenecker, Galatians, 7-8).
The gospel is not just soteriological but eschatological. God rescues us out of this present evil age. The preposition "out of" or "from" (ἐκ) is reinforced by the compound verb "rescue" (ἐξ-έληται). Christ came to rescue us out of one age for another age. The word "age" (αἰῶνος) introduces an eschatological component to the gospel. Paul and the other New Testament writers believed a two-age doctrine of history, this present age and the age to come. The two-age doctrine was common in Jewish thinking by this time as well. (Burton, Galatians, 426-432). The dawning of the Messianic age was the great expectation of Jews and Christians alike. Jesus, the Messiah, came preaching this good news (Mark 1:14-15). Paul was still preaching the kingdom of God at the end of Acts (28:31), and we continue to preach this good news today.
Christ came to rescue us from "the age" (τοῦ αἰῶνος) which Paul describes as "present" and "evil" (τοῦ ἐνεστῶτος πονηροῦ). The single article (τοῦ) governs both descriptors (Blass/Debrunner, Grammar, 141) to give the full weight of significance to the age from which we are rescued. The participle translated "present" (ἐνεστῶτος) is in the perfect tense referring to a state which has begun and continues to exist (Burton, Galatians, 432). The expression "this present age" (τοῦ αἰῶνος τοῦ ἐνεστῶτος) finds a parallel in Romans 12:2 where Paul exhorts us not to be conformed to "this age" (τῷ αἰῶνι τούτῳ).
The adjective "evil" (πονηροῦ) is in the position of emphasis in this clause making the primary characteristic of this age not merely a time period but a way of life. Sometimes Paul uses age (αἰών) and world (κόσμος) synonymously to emphasize the world system in which we currently live. We are not removed from the world. We are rescued from its power (Longenecker, Galatians, 8-9). Our present age is an age of evil in contrast with the Messianic age to come. We should expect wickedness to dominate the world from which Christ rescues us. We must not fall in love with this world system. The gospel proclaims that we are rescued from the power of this present evil age not the presence of evil in this age.
This verse may well be the earliest written statement about the significance of the death of Christ for our lives (Bruce, Galatians, 77). If so, the death of Christ is framed from the beginning in cosmic terms. The early Christians viewed themselves as "living on the frontier of two aeons, the Gospel transferring them as it were across the border" (Lightfoot, Galatians, 74). The sense of time is lost in the force of moral reality. Time stands still. We live now on the border between two worlds, plucked out of one world into another. The Gospel is the great news that we belong to one side of that border even as we face the other side in battle. We eagerly await the day when this present evil age ends, and we live forever in the age to come.
Brothers and sisters in Christ, let's proclaim the BIG gospel!