How do we know sanctification is by grace?

Sanctification cannot be achieved by strict adherence to the law; rather, it is a work of God's grace in the life of the believer. As Paul explains in Galatians 5:1, believers are called to stand fast in the liberty Christ has given them, which is opposed to the bondage of the law. The believer's life is transformed and sanctified through the grace of Christ that dwells within, not by external law enforcement. This principle highlights the power of grace and emphasizes that true holiness flows from a relationship with Christ, rather than from ritualistic law keeping.