How do we know Jesus' atonement is true?

The assurance of Jesus' atonement being true is grounded in the authority of Scripture, which provides the foundational truth of His mission. In John 17:4-5, Jesus explicitly states His fulfillment of the task given by the Father, signaling the reality of His sacrificial work. The prophetic prefigurations in the Old Testament, pointing towards the coming Messiah, further affirm this truth. Through Christ’s life, death, and resurrection, He has validated that He is indeed the Lamb of God who takes away the sin of the world, as seen in passages throughout the Gospels and corroborated by the Apostles' teachings.

Furthermore, this historical reality underscores the sovereign grace of God, wherein the specific people He intended to redeem are guaranteed eternal security through the work of Christ. Historic Reformed theology maintains that since Jesus' atonement is effective and sufficient for those whom He purposed to save, believers can rest assured in its truth, supported by the testimonies of the Spirit and the church throughout the ages.