How do we know Christ's atonement is sufficient for salvation?

The sufficiency of Christ's atonement is rooted in its completeness and finality. Hebrews 9:11-12 points out that Christ, as our high priest, entered the heavenly sanctuary with His own blood, securing eternal redemption for His people. This contrasts with Old Testament sacrifices, which required repeated offerings. Christ's singular sacrifice, as described in Romans 5:10, reconciles us to God while we were still enemies, reaffirming that His atonement is effective for all who believe. Therefore, any reliance on human works for salvation undermines the all-sufficiency of Christ's sacrifice.