Galatians is a gift that keeps on giving. The gospel might be simple enough for a child, but there is depth and nuance that rewards careful and repeated study of the Scriptures - especially when done with a friend, with a cup of the finest coffee for a couple of hours.
1. Departure from the gospel is (1v6) to desert him who called us in Christ. Which is to say that to have faith in the gospel is to be in relationship with the Father by being in Christ. Opposing sound doctrine is to set yourself against Christ and his Father. Heresy defames and derides and dishonours Christ. The gospel is the Father's welcome to the divine family.
2. Departure from the gospel is to be severed from Christ (5v4). Which is to say that to have faith in the gospel is (4v19) to have Christ formed in you. Clothed in Christ, indwelt by Christ, baptised into Christ. The gospel is Christ's welcome to the divine family.
3. Departure from the gospel is to turn from the Spirit with whom you began (3v3). Which is to say that to have faith in the gospel is to have the Spirit cry Abba Father from your heart to the Father (4v6). The gospel is not a faith we adopt so much as the good news of the God who will adopt us. The gospel is the Spirit's welcome to the divine family.
4. Departure from the gospel is to draw back from those who belong in God's family (2v12). Which is to say that to have faith in the gospel is to be united with all those who Christ welcomes whatever culture, gender or class (3v28). Flesh divides, external markers and standards to achieve exclude - faith supremely includes. The gospel is welcome to the divine family, by belonging to the church locally and globally.
In the language of Paul's letter to the Galatians, the gospel is a word to hear with faith (3v2) saying: on the basis of the curse-bearing, blessing-bringing, meaning-filled crucifixion of Jesus Christ you are welcome into the life of the Triune God.