How do we know that salvation is entirely through Christ?

The sermon emphasizes that salvation cannot be achieved by human effort or merits; it is wholly dependent on Christ's righteousness. This is rooted in the Reformed belief that God's law must be fulfilled perfectly, which only Christ, as both God and man, can do. His sacrificial death on the mercy seat serves as the definitive action that satisfies divine justice, enabling believers to rest in the assurance that they are perfect in God's sight through Him. Therefore, the certainty of salvation rests not on human action but on Christ's finished work.