How do we know that Christ's propitiation is effective for us?

The Scripture assures us that Christ's propitiation applies specifically to His elect—those who have been given faith and the gift of repentance. The effectiveness of His atoning work is tied to our belief in Him, as seen in John 1:12-13, where receiving Christ equates to being granted the right to be called children of God. Therefore, if one believes in Christ and repents of their sins, that serves as evidence that Christ's propitiation indeed covers them, guaranteeing their salvation.