Here's How to Have Full Assurance of Your Faith
Love flows from saving faith. Yet the sole basis of our salvation and assurance lies outside of us. In real history, Christ died in our place and by the Spirit imputes his righteousness to us. So God sees us as he sees Christ. Christ is the sole basis of our salvation and assurance.
We may feel doubt. But doubt cannot be real in Reformed theology because Christ in real history attained our justification for us and for our salvation. We receive him in faith. Christ totally becomes ours. No subjective doubt can gainsay the reality that we are just in Christ.
Satan uses the fear of judgement to entice us to sin. So subjective doubt bespeaks bedevilment. But in history, Jesus secured without fail our justification before God. Receiving Christ is all that matters. Doubt yourself perhaps; never doubt God in Christ.
Whenever we look to ourselves, we will invariably see sin and failure. The more mature the Christian, the more sin he or she perceives. So assurance never comes from an inward gaze—or if it does, then it is self-deception.
And yet saving faith pours out love, the fulfillment and summary of the law. But that love never justifies or else we would be justified by the law since love fulfills the law. So love flowing from faith evinces the Spirit's work in our hearts. God has shed him abroad in our hearts through faith.
So faith alone justifies and Christ alone provides assurance, yet all Christians will measure by measure manifest love by the Spirit. John Calvin explains, "It is therefore faith alone which justifies, and yet the faith which justifies is not alone." Faith always accompanies good works. But good works never justify nor assure—or else our assurance would rely on us not him who died for us.
What if we do not see the love of the Spirit in our lives? Do we doubt? Do we fear that God still sees us as an enemy? Never! "Follow not the judgment of reason, which telleth thee," writes Martin Luther, "that [God] is angry with sinners; but kill reason and believe in Christ."
It's time to make war on doubts. Yes, we all encounter down days. We all doubt. But our doubts add nothing to our salvation or lack thereof. Our salvation relies completely on the resurrection of Jesus for our justificaiton—providing the dual grace of remission of sins and imputation of Christ's righteousness.
Nothing else matters but our marriage to Christ, the clothing of the new man, that beautiful and wonderful exchange whereby Christ becomes ours fully. He imputes his righteousness to us. Then we fellowship with him by faith and spiritual union.
Deny doubt. Resist the devil's bedevilling lies. And "kill reason and believe in Christ."