The work of Christ on our behalf actually creates confidence and assurance; it is a source of assurance. The more we understand it, embrace it, and cherish it, the greater our sense of confidence and assurance will be.
Union with Christ
I have a teenage son who plays basketball. Recently, his coach recommended that he start going to the gym and lifting some light weights. So occasionally my son has been accompanying me to the gym where I’m a member and doing workouts with me. But here’s the thing: my son isn’t a member of the gym. When we walk up to the desk, I’m the one who calls up the membership information on my smartphone and buzzes us into the gym. And when I do, I point to my son and explain that he’s with me, and the attendant nods and waves us through.
Once that’s done, though, my son is free to do anything I’m free to do in the gym. Whatever equipment I’m authorized to use by virtue of my paid membership, he’s authorized to use because he’s there with me. Whatever privileges I have—to use the locker room, the pool, the weights, the basketball court—he shares them all because he’s with me. I have access to the gym by right of a paid membership; he has access to it not at all by right but by virtue of his relationship with me. What does all this have to do with your assurance of salvation? Everything in the world.
Confidence in Christ
Take a look at Hebrews 10:19-22:
Therefore, brothers, since we have confidence to enter the holy places by the blood of Jesus, by the new and living way that he opened for us through the curtain, that is, through his flesh, and since we have a great priest over the house of God, let us draw near with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.
This passage is all about having access to God’s presence—that is, having a right to stand before Him. Thus, the author of Hebrews writes that we as Christians should “have confidence” to enter into God’s presence, and we should “draw near” to Him, not with an “evil conscience”—that is, with fear that we don’t belong or that we’ll be cast out—but “in full assurance of faith.” That’s the goal—to stand in the presence of God and enjoy His blessings with full assurance and confidence that we belong there.