‘For you are all sons of God through faith in Christ Jesus.'
For having responded to Christ we are accepted as righteous in God's sight and are thus adopted as full grown sons, sons who have reached maturity, a sonship received ‘in Christ Jesus', through faith. This will be expanded on shortly (Galatians 4:4-7). We are thus free from all restraint except the restraint of sonship. We are no longer children subjected to rules and regulations, but like Abraham full grown sons who respond to the Father, because we are ‘in Christ' and through faith have become one with Him. We no longer need restraints. As grown up sons we want to please our Father.