“I used to have a struggle with sin, but not anymore,” the man said.

We were talking about assurance.

He was explaining that his past struggles with addictive substances had caused him to doubt his salvation. How could he be saved if he was getting drunk all the time? But since he had overcome drunkenness, doubts about his assurance had settled down. He was pretty sure he was saved.

But why?

Surely, he wasn’t sinless!

He said, “I used to have a struggle with sin,” but my thought was, “You will struggle with sin until the day you die.”

If you don’t believe me, think of Paul’s definition of love in 1 Corinthians 13:

Love suffers long and is kind; love does not envy; love does not parade itself, is not puffed up; does not behave rudely, does not seek its own, is not provoked, thinks no evil; does not rejoice in iniquity, but rejoices in the truth; bears all things, believes all things, hopes all things, endures all things. Love never fails (1 Cor 13:4-8a).

How does your love measure up to that standard? Are you ever mean, envious, puffed up, rude, self-seeking, provoked, impatient, distrustful, unfaithful, pessimistic, or defeatist? Then you’ve sinned! And if you ever struggle to meet the standard of love in 1 Cor 13:4-8a, then you struggle with sin!

Of course, your struggle with those sins might not be as public and as socially debilitating as struggling with substance addiction, but if you’re basing your assurance on how well you’re doing, your conscience should be just as troubled, because love sums up the Law (Matt 22:40), and if you’re not loving, you’re breaking the law just as surely.

Here’s the choice: you can have sin-based assurance or promise-based assurance.

I call it sin-based assurance because, in that view, assurance depends on measuring the amount of sin in your life. It’s not really about looking for good works. It’s about avoiding big sins. Since the amount of sin in your life is never “zero,” assurance depends on having only a “little” bit of sin. A little is okay. A little is compatible with really being born-again. If you’re only committing a little sin, then you can be “pretty sure” that you’re saved.

Except that’s not assurance, is it?

“Pretty sure” is not certainty. “Pretty sure” is the flipside of “kinda not sure.” If someone says, “I’m pretty sure I’m saved,” what that person is saying is, “But I’m kinda not sure that I’m saved, too.”

And no wonder! Sin-based assurance is a tightrope walk of being afraid of committing big sins (wherever that standard came from) and being unaware that “whoever shall keep the whole law, and yet stumble in one point, he is guilty of all” (Jas 2:10). That tightrope walk will end in disaster eventually!

So what’s the alternative to sin-based assurance?

Promise-based assurance.

Sometimes you not only have to take Jesus at His word—you must also take it as the last word. And that’s what Jesus’ promise of eternal life is—it is the last word on your salvation. Jesus gives eternal life to believers (John 3:16, 36). If you believe, or have ever believed, then you have eternal life.

The fact that you’re a sinner who has sinned, who sins, and who will keep on sinning is no barrier to your salvation and no proof that you aren’t born again, because salvation, along with assurance of salvation, is not about your faithfulness to Him, but about His faithfulness to His own promise, and He cannot deny Himself (2 Tim 2:13).