Introduction
Among the most demanding commands Jesus ever gave His disciples is the command to forgive. Forgiveness is not difficult merely because it requires relinquishing resentment; it is difficult because it confronts the deepest instincts of fallen humanity. When wounded, people naturally seek vindication, repayment, and justice on their own terms. Yet Christ repeatedly commands His followers to forgive, even when offences are repeated and costly.
Two passages stand prominently within Jesus’ teaching on forgiveness: Matthew 18:21–35 and Luke 17:3–10. These accounts are often studied independently, but when read together they provide a remarkably comprehensive theology of forgiveness. Matthew answers the question, Why must believers forgive? Luke answers the question, How are believers able to forgive? Matthew focuses on the immeasurable grace already received from God, while Luke focuses on the faith required to exercise forgiveness and the obedience demanded by Christ. Together they reveal that Christian forgiveness is a grace-enabled act of faith-filled obedience grounded in God’s prior forgiveness of sinners.
The Challenge of Forgiveness
Peter’s Question
In Matthew’s Gospel, Peter approaches Jesus with what likely appeared to him to be a generous proposal:
“Lord, how often will my brother sin against me, and I forgive him? As many as seven times?” (Matt. 18:21)
Peter assumes that forgiveness has limits. Even his suggestion of seven times reflects an attempt to exceed common expectations of mercy.
Jesus responds:
“I do not say to you seven times, but seventy-seven times.” (Matt. 18:22)
Jesus is not establishing a numerical limit but removing limits altogether. Forgiveness within the kingdom of God is to be characterised by a disposition of continual mercy.
To explain why this is so, Jesus immediately introduces a parable.
The Parable of the Unforgiving Servant
The Magnitude of Divine Mercy
The servant in the parable owes the king ten thousand talents—an incomprehensible amount that he could never repay. The debt symbolises humanity’s immeasurable guilt before God.
Unable to pay, the servant pleads for mercy.
Unexpectedly, the king does more than grant additional time. He completely forgives the debt.
The servant’s future is transformed entirely by grace.
The emphasis is unmistakable: salvation is not earned, negotiated, or repaid. It is received through divine mercy.
The Failure to Extend Mercy
Yet the forgiven servant immediately encounters another servant who owes him a comparatively insignificant amount.
Instead of extending the mercy he has received, he demands repayment and has the man imprisoned.
The king’s response reveals the heart of the parable:
“Should not you have had mercy on your fellow servant, as I had mercy on you?” (Matt. 18:33)
The issue is not merely that the servant acted harshly. His refusal to forgive demonstrates that he has failed to grasp the magnitude of the mercy shown to him.
Matthew’s central lesson is therefore clear:
Believers forgive because they themselves have been forgiven.
Luke’s Complementary Perspective
The Command to Repeated Forgiveness
Luke records a similar teaching concerning forgiveness:
“If your brother sins against you seven times in the day, and turns to you seven times, saying, ‘I repent,’ you must forgive him.” (Luke 17:4)
Like Matthew 18, the emphasis is on repeated forgiveness.
Yet Luke records a response from the disciples that Matthew does not include.
Immediately after hearing this command, they cry:
“Increase our faith!” (Luke 17:5)
This response reveals that they understand precisely what Jesus is demanding.
They do not question the command.
They question their ability to obey it.
The Relationship Between Forgiveness and Faith
Why the Disciples Request More Faith
The disciples recognise that forgiving repeatedly is not natural.
Human nature can perhaps forgive once.
It struggles to forgive repeatedly.
The command exposes human weakness.
Consequently, the disciples assume they require a greater measure of faith before they can obey.
Their request reveals a common assumption among believers:
“I would obey if only I possessed more faith.”
Jesus’ answer challenges this assumption.
The Meaning of the Mustard Seed
Jesus replies:
“If you had faith like a grain of mustard seed, you could say to this mulberry tree, ‘Be uprooted and planted in the sea,’ and it would obey you.” (Luke 17:6)
This statement is often interpreted as teaching that a small amount of faith can accomplish great things. While this is true, Jesus’ deeper point concerns the nature and object of faith.
The disciples are concerned with quantity.
Jesus redirects their attention to God’s sufficiency.
The Object of Faith
Faith derives its effectiveness not from its own strength but from the reliability of its object.
A weak person standing upon solid rock is secure.
A strong person standing upon thin ice is not.
The crucial issue is not the strength of the individual but the strength of that upon which he stands.
Similarly, the power of faith does not reside within faith itself.
It resides in God.
The disciples are asking:
“How much faith do we need?”
Jesus effectively responds:
“You are asking the wrong question.”
The issue is not how much faith they possess but whether they trust the God who commands forgiveness.
The focus shifts from faith itself to the God who is the object of faith.
Forgiveness as an Act of Trust
When believers forgive, they are exercising faith in several divine realities.
They trust:
God’s justice rather than seeking personal vengeance.
God’s wisdom rather than their own understanding.
God’s sovereignty over painful circumstances.
God’s promise to vindicate righteousness.
God’s grace to sustain obedience.
Forgiveness therefore becomes far more than an emotional decision.
It becomes an act of faith.
To forgive is to trust God with what one can no longer control.
Sufficient Grace and Sufficient Faith
Jesus Does Not Grant More Faith
A striking feature of Luke’s account is what Jesus does not do.
The disciples ask for increased faith.
Jesus does not tell them to wait until greater faith arrives.
Instead, He points them toward the faith they already possess.
This suggests an important theological principle.
The command itself assumes that God has already supplied sufficient grace for obedience.
Grace Precedes Command
Throughout Scripture, divine commands are grounded in prior divine grace.
God redeemed Israel before giving the Law.
Christ saves sinners before commanding discipleship.
Paul consistently presents God’s saving work before calling believers to obedience.
Similarly, forgiveness is not commanded in a vacuum.
Believers have already:
received mercy,
received the Spirit,
received faith,
received grace.
The command to forgive rests upon resources God has already supplied.
Matthew and Luke Together
When the two passages are read side by side, a beautiful theological harmony emerges.
Matthew explains the basis of forgiveness.
Luke explains the means of forgiveness.
Matthew says:
Look at the greatness of the King’s mercy.
Luke says:
Trust the greatness of the King who showed mercy.
Matthew focuses on grace received.
Luke focuses on faith exercised.
Both are necessary.
Grace provides the foundation.
Faith provides the instrument.
Obedience provides the expression.
The Parable of the Servant in Luke 17:7–10
Immediately after speaking about faith, Jesus tells another parable.
A servant works in the field all day.
Upon returning home, he does not expect praise for doing what he was commanded.
Instead, he simply fulfils his duty.
Jesus concludes:
“We are unworthy servants; we have only done what was our duty.” (Luke 17:10)
At first glance this seems unrelated to forgiveness.
In reality, it completes Jesus’ teaching.
The sequence is significant:
Forgive repeatedly.
Exercise faith.
Obey the command.
Do not seek recognition for obedience.
Forgiveness is not portrayed as spiritual heroism.
It is portrayed as faithful service.
Believers forgive because their Master commands it.
A Reformed Theological Perspective
The Reformed tradition has consistently emphasised that God’s commands are accompanied by God’s enabling grace.
John Calvin argued that God never intends His commands to drive believers toward self-sufficiency but toward dependence upon divine grace.
Similarly, John Owen taught that every act of Christian obedience is produced through the work of the Holy Spirit within the believer.
Forgiveness is therefore not:
natural virtue,
emotional strength,
moral superiority.
It is grace producing obedience through faith.
Likewise, R. C. Sproul frequently emphasised that faith is effective not because of its magnitude but because of the greatness of the God in whom it rests.
The mustard seed teaches that even weak faith can accomplish God’s purposes because God’s power, not man’s faith, is decisive.
 The Gospel Dynamic of Forgiveness
The unified testimony of Matthew 18 and Luke 17 reveals a profound gospel pattern.
The believer remembers the immeasurable debt forgiven by God.
The believer trusts the God who commands forgiveness.
The believer obeys the command through grace-enabled faith.
Thus forgiveness involves three inseparable realities.
First, Memory of Grace
We remember the ten-thousand-talent debt.
We were forgiven infinitely more than we will ever forgive.
Second, Exercise of Faith
We trust God’s wisdom, justice, and sufficiency rather than our feelings and instincts.
Third, Obedient Submission
We forgive because Christ commands it, recognising that faithful servants simply obey their Master.
Conclusion
Matthew 18:21–35 and Luke 17:3–10 together present one of the fullest New Testament portraits of forgiveness. Matthew reveals why believers must forgive: because they have received immeasurable mercy from God. Luke reveals how believers can forgive: through faith in the God whose grace is sufficient for every act of obedience. The concluding servant parable in Luke further teaches that forgiveness is not an extraordinary achievement deserving recognition but the ordinary duty of those who belong to Christ.
Taken together, these passages suggest that believers are not waiting for additional grace before forgiving. The grace has already been given. The faith required has already been supplied. The command has already been spoken. The question is not whether God has provided sufficient resources for forgiveness, but whether believers will trust the God who forgave them and obey the Master who commands them.
In this way forgiveness becomes one of the clearest demonstrations of the gospel itself: grace received, faith exercised, and obedience rendered to the glory of God.
Soli Deo Gloria