How do we know that Jesus' atonement is sufficient?

The sufficiency of Christ's atonement is primarily rooted in the understanding that His sacrifice was made once for all, as portrayed in Hebrews 9:12. Unlike the repetitive sacrifices of the Levitical priesthood, which could never truly atone for sin, Christ’s offering is perfect and final. He paid the debt of sin in full, meeting the claims of justice required by the law.

Moreover, this sacrifice grants believers eternal redemption, affirming that their sins are entirely cancelled, as seen in passages like Romans 8:1, where there is no condemnation for those in Christ. The assurance of salvation through His atonement is not based on human merit but on the merits of Christ's blood, which continually speaks on our behalf in the heavenly realm.