The Calculus of Grace: Stumbling, Forgiveness, and Duty Text: Luke 17:1-10
Introduction: The Unsentimental Demands of Discipleship
We live in a soft age, an age that likes its Christianity served warm, with a side of therapeutic affirmation. We want a Jesus who is endlessly affirming and never demanding, a faith that is all comfort and no cost. But the Jesus we meet in the Gospels, and particularly in this passage from Luke, is not a sentimentalist. He is a king, and He is a commander. He lays down the law of His kingdom, and the terms are stark, severe, and glorious. He speaks of millstones, of radical forgiveness, of mountain-moving faith, and of unprofitable servanthood. This is not the language of a life coach trying to help you find your best self. This is the language of a sovereign Lord calling His people to a radical, world-altering discipleship.
The world around us is obsessed with two things: personal offense and personal autonomy. We are taught to nurse our grievances like precious heirlooms and to view any demand on our lives as an intolerable imposition. "You do you" is the great commandment of our time. Into this cultural soup, Jesus' words land like a meteor. He tells us that causing another to sin is a capital crime in the court of Heaven. He commands a forgiveness so relentless it seems mathematically impossible. And He concludes by reminding us that even if we were to do all this perfectly, we would still just be doing our job. We would have no room for boasting, no ground for self-congratulation.
This passage is a direct assault on our pride. It attacks our pride in being offended, our pride in our supposed limitations ("I just can't forgive that"), and our pride in our accomplishments. It forces us to confront the immense gravity of sin, the supernatural nature of forgiveness, and the fundamental reality of our relationship to God. We are not His business partners. We are not consultants He has brought in for a special project. We are His slaves, bought with a price, and our only reasonable service is total, uncalculating obedience.
So as we walk through this text, we must ask the Spirit to strip away our modern sensibilities. We must come to it not as consumers looking for a spiritual product that meets our felt needs, but as soldiers reporting for duty, ready to receive our marching orders from our commander-in-chief. For in these demanding words, we find not a burden, but the only true path to liberty.
The Text
Now He said to His disciples, “It is inevitable that stumbling blocks come, but woe to him through whom they come! It would be better for him if a millstone were hung around his neck and he were thrown into the sea, than that he would cause one of these little ones to stumble. Be on your guard! If your brother sins, rebuke him; and if he repents, forgive him. And if he sins against you seven times a day, and returns to you seven times, saying, ‘I repent,’ forgive him.” And the apostles said to the Lord, “Increase our faith!” And the Lord said, “If you have faith like a mustard seed, you would say to this mulberry tree, ‘Be uprooted and be planted in the sea’; and it would obey you. But which of you, having a slave plowing or tending sheep, will say to him when he has come in from the field, ‘Come immediately and sit down to eat’? But will he not say to him, ‘Prepare something for me to eat, and, clothing yourself properly, serve me while I eat and drink; and afterward you may eat and drink’? Is he grateful to the slave because he did the things which were commanded? In this way, you also, when you do all the things which are commanded of you, say, ‘We are unworthy slaves; we have done only that which we ought to have done.’ ”
(Luke 17:1-10 LSB)
The Gravity of Stumbling Blocks (vv. 1-2)
Jesus begins with a solemn warning about the certainty of sin and the severe consequences for those who facilitate it.
"Now He said to His disciples, “It is inevitable that stumbling blocks come, but woe to him through whom they come! It would be better for him if a millstone were hung around his neck and he were thrown into the sea, than that he would cause one of these little ones to stumble." (Luke 17:1-2)
First, notice the realism of Jesus. He says it is "inevitable" that stumbling blocks come. The Greek word is skandalon, from which we get our word scandal. It refers to a trap, a snare, something that trips a person up and causes them to fall into sin. In a fallen world, populated by fallen people, this is a given. Jesus is not a utopian idealist. He knows the score. Sin will happen. People will be tempted. Offenses will come.
But this inevitability does not lessen the responsibility of the one who lays the trap. "Woe to him through whom they come!" The fact that sin is predictable does not make it excusable. And the judgment Jesus describes is terrifyingly graphic. It would be better to have a donkey-driven millstone, a massive stone weighing hundreds of pounds, tied to your neck before being tossed into the sea. This is not hyperbole for hurt feelings. Jesus is talking about causing one of "these little ones" to stumble. This refers not just to children, but to new believers, weak believers, those who are spiritually vulnerable. To lead such a person into sin, to damage their conscience, to shipwreck their faith, is an act of such profound spiritual violence that a swift, brutal death would be preferable to facing the wrath of God for it.
This is a direct rebuke to our casual attitude toward sin. We live in a culture that treats sin as a lifestyle choice. We tolerate false teachers who tickle ears and lead the flock astray. We excuse our own "small" sins of gossip, slander, or hypocrisy, forgetting that these things can be deadly stumbling blocks to a brother or sister watching us. Jesus is telling us that our personal holiness has profound corporate implications. Your sin is never just about you. It creates ripples, and if those ripples cause a little one to drown, the millstone awaits.
The Radical Mathematics of Forgiveness (vv. 3-4)
From the gravity of causing sin, Jesus pivots to the mandatory response when we are sinned against.
"Be on your guard! If your brother sins, rebuke him; and if he repents, forgive him. And if he sins against you seven times a day, and returns to you seven times, saying, ‘I repent,’ forgive him." (Luke 17:3-4)
The command to "be on your guard" connects directly to what came before. We are to guard ourselves from causing others to stumble, and we are to guard ourselves from responding sinfully when we are sinned against. The first step is not to quietly nurse a grudge. It is to "rebuke him." This is not an angry outburst; it is a clear, courageous, and loving confrontation. To let a brother persist in his sin without rebuke is not kindness; it is a form of hatred (Leviticus 19:17). You are letting him walk toward a cliff without a warning.
But the rebuke is for the purpose of restoration. If he repents, the command is absolute: "forgive him." There are no other conditions. It is not "if he repents and you feel like it," or "if he repents and promises never to do it again." If repentance is present, forgiveness must be granted. And this is where Jesus turns up the heat. "Seven times in a day." This is not a literal quota. Seven is the biblical number of completion and perfection. Jesus is describing a pattern of relentless, ridiculous, scandalous forgiveness. He is describing a forgiveness that defies all our worldly bookkeeping and our sense of fairness.
Our natural response is to say, "But his repentance can't be sincere if he keeps doing it!" We want to be the inspectors of his heart, the judges of his sincerity. But Jesus does not give us that job. Our job is to take him at his word. If he says, "I repent," our job is to say, "I forgive." Why? Because this is how God treats us. How many times a day do we sin against God in thought, word, and deed? How many times do we come to Him, saying "I repent," only to stumble in the same way again? Our entire relationship with God is built on this scandalous, seven-times-a-day grace. To refuse it to a brother is to declare that we ourselves have no need of it, which is the ultimate lie.
The Logic of Faith (vv. 5-6)
The disciples' reaction to these commands is entirely understandable. They are overwhelmed.
"And the apostles said to the Lord, “Increase our faith!” And the Lord said, “If you have faith like a mustard seed, you would say to this mulberry tree, ‘Be uprooted and be planted in the sea’; and it would obey you." (Luke 17:5-6)
The apostles rightly diagnose the problem. They recognize that the kind of life Jesus is describing, a life of such careful holiness and radical forgiveness, is impossible in their own strength. It requires a supernatural resource. So they ask for more faith. They think the issue is quantitative. "We have a little faith, but for this, we're going to need a whole lot more."
But Jesus corrects their thinking. The issue is not the amount of faith, but the object of faith. It is not about the size of your faith, but the size of your God. "If you have faith like a mustard seed..." A mustard seed was proverbially the smallest of seeds. Jesus is saying that even a tiny amount of genuine faith, faith that is actually placed in the omnipotent God, can accomplish impossible things. The image of uprooting a mulberry tree, a tree known for its deep and extensive root system, and planting it in the sea is an image of radical impossibility. It is absurd.
The point is this: True faith does not look at the size of the obstacle (a deeply rooted tree, a seven-times-a-day sin) or at the size of its own resources (a tiny seed). It looks to the power of God. The apostles were looking at the difficulty of the command and the poverty of their own hearts. Jesus redirects their gaze. He is telling them that forgiving their brother seven times a day is not actually the hard part. The hard part is believing that the God who commands it is the same God who can make mulberry trees jump into the ocean. The commands to avoid causing stumbling and to forgive relentlessly are not suggestions for self-improvement. They are invitations to depend entirely on the supernatural power of God, a power that is unleashed by even the smallest particle of genuine faith.
The Posture of Duty (vv. 7-10)
Jesus concludes this section with a parable that seems, at first, to be disconnected. But it is, in fact, the foundation that makes all the rest possible. It defines our relationship to the one giving the commands.
"But which of you, having a slave plowing or tending sheep, will say to him when he has come in from the field, ‘Come immediately and sit down to eat’? But will he not say to him, ‘Prepare something for me to eat, and, clothing yourself properly, serve me while I eat and drink; and afterward you may eat and drink’? Is he grateful to the slave because he did the things which were commanded? In this way, you also, when you do all the things which are commanded of you, say, ‘We are unworthy slaves; we have done only that which we ought to have done.’ ” (Luke 17:7-10)
This is a hard teaching for modern ears. The word is doulos, slave. And the relationship is one of pure obligation. The slave works all day in the field, and when he comes in, his work is not done. He must then serve his master's dinner. He eats only after the master is satisfied. And the master is not obligated to thank him. Why? Because the slave has only done what he was commanded to do. He has only fulfilled his duty.
Jesus applies this directly to the disciples. "In this way, you also..." After you have perfectly obeyed the commands about stumbling blocks, after you have forgiven your brother seven times in one day, after you have exercised mountain-moving faith, what should your attitude be? It should be this: "We are unworthy slaves; we have done only that which we ought to have done." The word "unworthy" here means we have not accrued any extra merit. We haven't put God in our debt. We haven't done anything deserving of special thanks or reward. We have simply done our job.
This is the death blow to all pride and all spiritual scorekeeping. We cannot approach God on the basis of a transaction. We cannot say, "Lord, I forgave my brother seven times today, so now you owe me." No. All our obedience, every last bit of it, is simply our duty. We are owned by God, twice over. He created us, and when we sold ourselves into sin, He bought us back with the blood of His Son. Our lives are not our own. Therefore, obedience is not optional, and it is not meritorious. It is the baseline expectation.
And here is the glorious paradox. It is only when we embrace this identity as unworthy slaves that we can truly experience the freedom of the gospel. When we stop trying to earn God's favor, we are free to simply rest in the favor He has already given us in Christ. When we know that our standing with God depends entirely on Christ's performance and not our own, we are liberated to obey out of gratitude, not out of a desperate need to impress Him. The slave who knows he is utterly dependent on his master's grace is the one who can serve without anxiety, without pride, and without demanding thanks. He serves because he is a slave, and in the household of God, that is the most honored and liberated position to be in.
Conclusion: The Unprofitable Servant's Joy
So what do we do with these hard words? We must see them as a cohesive whole. The high demand for holiness (don't cause stumbling) and the high demand for forgiveness (seventy times seven) are impossible for us. This impossibility is meant to drive us to a cry for faith. And that cry for faith is answered when we understand that even the smallest faith connects us to an infinitely powerful God. But the engine that drives all of it, the thing that keeps us from turning our obedience into a new form of prideful works-righteousness, is the recognition that we are unprofitable servants.
We have only done our duty. But here is the wonder of the gospel. Our Master is not like the master in the parable. Though we are unprofitable servants who have only done what we ought, our Master, out of sheer, unadulterated grace, says to us, "Well done, good and faithful servant... Enter into the joy of your lord" (Matthew 25:21). He pulls up a chair for us. He serves us. He washes our feet. He treats us not as slaves, but as friends, as sons, as co-heirs.
The path to that glorious fellowship is the path of humble obedience. It is the path of taking sin seriously, both ours and others'. It is the path of forgiving as we have been forgiven. And it is the path of recognizing that everything we do for Him is nothing more than our basic, fundamental duty. When we live this way, we find that the yoke is easy, and the burden is light. For the slave of such a gracious Master is the freest man in the world.