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

The effectiveness of Christ's sacrifice for salvation is rooted in its ability to fully satisfy God's justice, which is necessary for reconciliation with a holy God. Romans 5:9 affirms that 'we shall be saved from wrath through Him.' This means that due to the redemptive work accomplished on the cross, God's anger towards sin has been fully appeased. Charnock elaborates that Christ, being both fully divine and fully human, offered the only sacrifice that could bear the weight of all the sins of mankind, ensuring that justice was met without compromising God’s holiness. It was through this perfect sacrifice that believers are declared righteous and welcomed into eternal fellowship with God as a result. Therefore, the confidence in the efficacy of Christ’s sacrifice rests not on human merit but on God's sworn promise and truthfulness.