How do we know that Jesus' sacrifice has accomplished salvation?

The assurance of salvation is rooted in the finished work of Christ, as declared in John 19:30 when Jesus said, 'It is finished.' This proclamation signifies that He completed the work assigned to Him by God the Father—to redeem a people for Himself. The means of this redemption was His sacrificial death on the cross, where He bore the wrath of God for sin and fulfilled the law in perfect obedience. This accomplishment underpins the Reformed understanding that salvation is entirely a work of God's grace, unemebellished by human effort. Believers can rest in the assurance that their sins are forgiven not because of their works, but because of Christ's perfect sacrifice.