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

The effectiveness of Christ's atonement is seen in the historical act of Him purging our sins, which is affirmed in Hebrews 1:3. When He sat down at the right hand of the Majesty on High, it signified that the work was finished and accepted by the Father. This positions Christ not only as the Savior but also as the high priest who intercedes for His people. The testimony of Scripture assures us that His sacrifice fully satisfied divine justice, leading to the reconciliation of sinners to God. This truth is further confirmed by passages such as Romans 8:34, which affirms that if Christ is the one who justifies, then there is no condemnation for those for whom He died.