“I believe; help my unbelief!” (Mark 9:24). This plea — this prayer — of a desperate father, who was interceding to Jesus on behalf of his afflicted child, expresses in five simple words a profound, difficult, confusing, and common experience. All followers of Jesus have both belief and unbelief, both faith and doubt, present in us at the same time.

We see this paradoxical presence elsewhere in Scripture. We see it in Peter, who walked on water only to start sinking when unbelief set in (Matthew 14:28–31). We see it in Thomas, who declared, “I will never believe” without physical proof of Jesus’s resurrection, while still believing enough to stay with the other disciples until Jesus finally appeared to him (John 20:25–26). We see it laced through the Psalms, like Psalm 73, where saints wrestle out loud with their unbelief. And we see it all too frequently in ourselves, which is why we identify with the desperate father’s prayer. Unbelief is a “common to man” temptation for believers (1 Corinthians 10:13).

But though it is a common temptation (and often a subtle temptation), it is a spiritually dangerous one, one that can lead us “to fall away from the living God” (Hebrews 3:12). It is an enemy we must fight vigorously.

“Do not fear God’s discipline; fear unbelief.”

We each fight unique battles against this enemy, because each of us has unique experiences and unique temperaments that make us uniquely vulnerable to certain forms of unbelief. Getting help to see our vulnerabilities to unbelief is crucial to winning our battles. And it is something Jesus is happy to help us with, if we ask him.

Desperate and Vulnerable Father

The father of the afflicted boy in Mark 9:14–29 surely had a unique vulnerability to unbelief. And it’s not difficult to understand why. Just imagine what his experience had been like up to the point when he encountered Jesus.

He had spent a number of years, likely doing everything he could, in order to help his son (Mark 9:21). The terrible affliction had a demonic source, which had tormented the boy since early childhood, causing violent seizures and preventing him from speaking (Mark 9:17–18). The father, and no doubt his wife, had saved their precious child — their only begotten son (Luke 9:38) — from death numerous times, rescuing him out of fire and water (Mark 9:22). Which means they lived with the daily dread that they might not be there in time to save him the next time. And they lived with the future dread of what would become of him when one or both were no longer there to save him.

They also likely lived with a deep fatigue brought on by continual vigilance night and day. They may have endured a kind of recurring relational strain on their marriage that often accompanies stressful and painful parenting situations. They likely lived with the numerous ways their son’s affliction affected them financially, from the direct costs of seeking out help for him, to the indirect costs of having less time devoted to earning a living. And on top of all that, they likely lived with the shame that perhaps they, or their child, had somehow sinned and brought this curse upon the boy — a shame compounded by knowing that others likely wondered the same thing (as in John 9:1–2).

Unique Battles in a Common War

Surely this beleaguered father had prayed often for his priceless son, but with no visible results. Surely he had previously sought out other spiritual leaders or exorcists to drive the devil out, but to no avail.

Hearing stories of Jesus’s power over disease and demons stirred in him enough hope that he brought his child to see Jesus. Not finding the famous rabbi, he pleaded with Jesus’s disciples for help. But they were no more effective than anyone else had been (Mark 9:18). We can understand why his hope, and therefore his faith, seemed to be ebbing low when Jesus showed up.

The reason I say all this is to show how this father was very much like us. His unbelief had roots in his unique experience. So does ours. His fears and disappointments shaped his expectations. So do ours. He was vulnerable, in deeply personal places, to losing the fight for faith. So are we. We can sympathize with this man when he pleaded with Jesus, “If you can do anything, have compassion on us and help us” (Mark 9:22), because we’ve probably prayed or thought similar things.

We might expect Jesus to respond as gently and kindly to this desperate father as he did to the leper seeking healing, to whom Jesus, in pity, reached out and touched, saying, “I will; be clean” (Mark 1:40–42). But that’s not how Jesus responded.

Surprising, Merciful Rebuke

Jesus’s response to this father catches us off guard: “‘If you can’! All things are possible for one who believes” (Mark 9:23). This shocks us. And the reason is because most of us can identify more with the father’s struggle than with the leper’s. We expect Jesus to comfort this man, but instead he rebukes him. It makes us wonder, Is this how Jesus feels about our unbelief?

“All of us who believe in Jesus also have unbelief in Jesus.”

One way to answer is that, in the Gospels, Jesus consistently affirms those who express faith and rebukes those who express doubt and unbelief. The leper he healed is a good example. This man said to Jesus, “If you will, you can make me clean” (Mark 1:40). This is a declaration of faith, and it moved Jesus to a compassionate response of healing.

But the father of this afflicted boy said to Jesus, “If you can do anything, have compassion on us and help us” (Mark 9:22). There’s faith in this request; faith is why he sought Jesus out in the first place. But there’s also unbelief; part of him doesn’t expect Jesus will be any more successful than others had been. So, he receives Jesus’s rebuke, just like Peter did in the water and Thomas did when Jesus finally appeared to him (Matthew 14:31; John 20:27–29).

And here’s what we need to remember: Jesus’s rebuke to a believer who is allowing unbelief to infect and enfeeble his faith and govern his behavior is a great mercy.

Mercy of Discipline

Faith is the channel through which God’s graces of salvation and sanctification and spiritual gifts all flow. Unbelief obstructs the channel and therefore inhibits the flow of God’s grace (James 1:5–8). So, Jesus’s rebuke of the man’s unbelief is the mercifully painful, momentary discipline of the Lord intended to expose the disease of unbelief (to use a different metaphor) so the believer can see it for what it is and fight it; because if he doesn’t, he will not share the Lord’s holiness and will not bear the peaceful fruit of righteousness (Hebrews 12:10–11).

In that sense, Jesus is the good physician. He does not coddle doubt and unbelief, just like a good doctor doesn’t coddle cancer in a patient. If left invisible and untreated, it will kill. So, what Jesus is doing is helping this struggling father see clearly his sin of unbelief, just like he did for Peter and Thomas.

And it worked. We see this in the father’s desperate cry to Jesus: “I believe; help my unbelief!” And like Jesus pulling Peter out of the water, and showing Thomas his hands and side, he honored the father’s faith, however defective, and set the boy free (Mark 9:25–27).

Jesus Will Help You See Your Unbelief

All of us who believe in Jesus also have unbelief in Jesus. It’s not surprising, because we all live with deceitful indwelling sin (Hebrews 3:13). And we all live in a fallen, deceitful world. So, we all must frequently fight for faith (1 Timothy 6:12) by battling unbelief.

“Unbelief will block the channels of faith, it will rob you of joy, and, if undealt with, it will destroy you.”

But the presence of unbelief in us is often subtle. We don’t always see it clearly. It has roots in our unique experiences and in our unique temperaments, which make us uniquely vulnerable to its deceitfulness. Our doubts can seem to us understandable, even justifiable. But like all sin and fallenness, unbelief is spiritually dangerous. What we really need, even though we might prefer to avoid it, is for Jesus to mercifully help us see our unbelief, even if it means his momentarily painful discipline.

Having followed Jesus for decades, I have experienced his discipline numerous times, including recently. I have learned to even ask him to discipline me when I recognize the symptoms of unbelief (which, for me, are a lingering, shadowy presence of doubt and skepticism and self-pity and self-indulgence). I ask Jesus to discipline me, not because I enjoy the pain and humbling of the exposure of my unbelief, but because I want the joy of fully believing that God exists and is the rewarder of those who seek him (Hebrews 11:6). And I want the channel of his grace toward me unclogged. And so I pray with the psalmist,

Search me, O God, and know my heart!
     Try me and know my thoughts!
And see if there be any grievous way in me,
     and lead me in the way everlasting! (Psalm 139:23–24)

I have found that Jesus answers.

And he will answer you. He will answer the prayer, “I believe; help my unbelief!” And he’ll help you fight your unbelief by exposing it, that place you want to conceal. But do not fear his discipline; fear unbelief. Unbelief will block the channels of faith, it will rob you of joy, and, if undealt with, it will destroy you. The momentary pain of the discipline, however, is the path to greater joy, for it opens the channels to more of God’s grace — to more of God.