How do we know Jesus Christ accomplished salvation?

Salvation is accomplished through the work of Jesus Christ, who fulfilled the divine plan of redemption. The psalmist in Psalm 85 refers to God’s past actions (using the term 'hast'), indicating that salvation was secured far before Christ's physical existence but was manifest in His coming as the Lamb slain from the foundation of the world. This means that God’s plan was always oriented towards salvation, and every Old Testament prophecy points to Christ. His sacrificial death met the demands of God’s justice while simultaneously extending His mercy to the elect, proving that salvation is entirely the work of Christ, with no contribution from us.