Now that faith has come: Righteousness by faith was always in effect (see 3:6–9), but now, through Jesus Christ, the object of that faith and how people can receive it are clear.
we are no longer under a guardian: In Greco-Roman culture, a child who reached adulthood was no longer under a guardian's control and could govern themselves. Similarly, those who mature through faith in Christ are free from the law's guardianship. They follow Christ directly as he guides them through his word and Spirit.