How do we know Christ's sacrifice is the true propitiation?

The certainty of Christ's sacrifice as the true propitiation lies in its divine ordination before creation. Romans 3:25 states that God set forth Christ as the propitiation through faith in His blood, signifying that this was not an afterthought but part of God's eternal plan. Throughout the Old Testament, Christ was foreshadowed through sacrifices and prophecies, affirming His role as the Messiah appointed to take on the sins of the people. This underscores that the need for a real, effective sacrifice was known to God from the beginning, demonstrating both His justice in judging sin and His heart for mercy towards His chosen people.