How do we know that Christ's death was effective?

The effectiveness of Christ's death is encapsulated in Hebrews 1:3, which asserts that He "purged our sins" by His sacrificial death. This implies that the work of redemption is not incomplete or conditional; rather, it is definitive and effective for those whom He died for. Furthermore, Romans 5:10 reinforces this by explaining that when we were enemies, we were reconciled to God by the death of His Son, affirming that true reconciliation occurs through Christ's sacrifice, firmly establishing the impact of His atoning work.