The pursuit of assurance may last long. We may find, moreover, that doubt can return after a long season of confidence, for assurance once enjoyed does not mean assurance always enjoyed. Our peace can rise and fall, requiring a fresh pursuit of assurance through the means God has provided. But however long we have to travel this road, and however often, remember: the preciousness of assurance outweighs all the world.

Soon after becoming a Christian, I started wondering if I really was a Christian. The first doubt struck unexpectedly, like lightning from a cloudless sky. Am I real? I seemed to love Jesus. I seemed to trust him. I seemed to bear the marks of a changed life. But, the thought crept in, so too did Judas.

Though the long night of wrestling slowly passed, I emerged from it like Jacob, limping into the daylight. Assurance has been, perhaps, the main question, the chief struggle of my Christian life over the years, sending me searching for what Paul and the author of Hebrews call “full assurance” (Colossians 2:2; Hebrews 10:22).

The topic of assurance is complex, to put it mildly. Genuine Christians doubt their salvation for many different reasons, and God nourishes assurance through several different means. So the needed word for one doubter often differs from the needed word for another. Nevertheless, for those who find themselves floundering, as I did, perhaps unsure what’s even happening to them, a basic guide to assurance may prove useful.

Possibility of Assurance

By assurance, I simply mean, to borrow a definition from D.A. Carson, “a Christian believer’s confidence that he or she is in right standing with God, and that this will issue in ultimate salvation.” Assured Christians can say, with Spirit-wrought conviction, not only “Christ died for sinners” but “Christ died for me.” Though sin may assault them, and Satan may accuse them, they know themselves forgiven, beloved, and bound for heaven. And the first word to offer about such assurance is simply this: it’s possible.

Your faith may feel small, and your hold on Christ shaky. Even still, it is possible for you to feel down deep that he will never cast you out (John 6:37). It is possible for you to cry “Abba!” with the implicit trust of God’s children (Romans 8:15–16). It is possible for you to “rejoice with joy that is inexpressible and filled with glory” (1 Peter 1:8). It is possible for you to have “confidence for the day of judgment” (1 John 4:17) — indeed, to “know that you have eternal life” (1 John 5:13).

God’s desire for his people’s assurance, even for the most fragile of them, burns brightly through the Scriptures. He has knit assurance into his very name, whether old covenant (Exodus 34:6–7) or new (Matthew 1:21). He has spoken assurance in promise upon promise from a mouth that “never lies” (Titus 1:2). And as he once wrote assurance with a rainbow (Genesis 9:13–17), and flashed assurance through the stars (Genesis 15:5–6), so now he has sealed assurance with the greatest sign of all: the body and blood of his dear Son. Week by week, we eat the bread and drink the cup of his steadfast love in Christ (Matthew 26:26–29).

If God’s new covenant is sure (and it is), if his promises are true (and they are), and if his character cannot change (and it can’t), then full assurance is possible for everyone in Christ, no matter how strong our present fears.

Enemies of Assurance

If, then, Scripture testifies so powerfully to the possibility of assurance, why does anyone ever lack assurance — and why do some seem to struggle with it ongoingly? Because Christian assurance is not only possible, but opposed. Of the enemies that assail us, three are chief: Satan, sin, and our broken psychology.

Satan

We might expect “the accuser of our brothers, . . . who accuses them day and night before our God” to war against the Christian’s peace (Revelation 12:10). And so he does.

In his classic on assurance, Religious Affections, Jonathan Edwards reminds readers that the devil assaulted even the assurance of Jesus (172). “If you are the Son of God, command these stones. . . . If you are the Son of God, throw yourself down” (Matthew 4:3, 6). The Father had just said, “This is my beloved Son” (Matthew 3:17), but the devil loves to trade his own if for God’s is.

Many a true Christian has, in turn, heard that dreadful if: “If you are a Christian, why do you sin so much? Why is your faith so small? Why is your heart so cold?” And though Satan’s charges cannot condemn those whom God has justified (Romans 8:33), they certainly can ruin our comfort.

The devil knows that well-assured Christians threaten the domain of darkness more than any other. And so, he protects his property with one of his most-used weapons: doubt.

Sin

Alongside Satan, Scripture presents sin as one of the foremost enemies of assurance. Now, of course, assurance in this life always coexists with sin. “If we say we have no sin, we deceive ourselves, and the truth is not in us” (1 John 1:8). Nevertheless, habitual sin, unrepentant sin, or particularly grievous sin darkens our assurance as surely as drawn curtains darken a room — and it should.

“By this we know that we have come to know him,” the apostle John writes, “if we keep his commandments” (1 John 2:5). And therefore, when a pattern of commandment-keeping gives way to commandment-breaking, and a pattern of repentance to stubbornness, and a pattern of confession to secrecy, we cannot “know that we have come to know him” with the same confidence as before. We may be secure in Jesus’s grasp, as Peter was even when he denied his Lord, but our sense of that security is rightly weak until we “have turned again” (Luke 22:31–32), and again have heard his pardoning voice (John 21:15–19).

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