How do we know perseverance is evidence of true salvation?

In historic Reformed theology, perseverance is seen as a result of God's grace. The belief is that if someone is genuinely saved, their faith will manifest in a sustained commitment to Christ, even in the face of trials and persecution. The assurance of this comes from the understanding that it is God who began the good work in the believer and will carry it on to completion (Philippians 1:6). The failure to endure, according to Scripture, often indicates that a person was never truly saved (1 John 2:19), reinforcing that true salvation is accompanied by the grace that empowers endurance.