He said to his disciples, “Things that cause sin will inevitably occur, but woe to the person through whom they occur. 2 It would be better for him if a millstone were put around his neck and he be thrown into the sea than for him to cause one of these little ones to sin. 3 Be on your guard! If your brother sins, rebuke him; and if he repents, forgive him. 4 And if he wrongs you seven times in one day and returns to you seven times saying, ‘I am sorry,’ you should forgive him.”
5 And the apostles said to the Lord, “Increase our faith.” 6 The Lord replied, “If you have faith the size of a mustard seed, you would say to [this] mulberry tree, ‘Be uprooted and planted in the sea,’ and it would obey you.
Luke places these sayings on the road to Jerusalem, where Jesus teaches his disciples how to live as a community under God’s mercy. He warns against causing others to sin, commands honest correction and real forgiveness, and answers the apostles’ plea for stronger faith.
Jesus begins with a sober fact: occasions for sin will come. Human weakness and a fallen world make them “inevitable,” but no one is excused for leading others into sin. “Little ones” refers first to his disciples—the vulnerable, the newly converted, those who trust him. To harm their faith is a grave offense. The image of a millstone and the sea speaks of something worse than death. It underlines how serious it is to push another into sin by bad example, false teaching, or calculated pressure.
He then turns to life inside the community. “Be on your guard” means watch your own heart and watch over your brother. If your brother sins, you must rebuke him. This is not harshness. Scripture already binds love to correction: “You shall reprove your neighbor, or you will incur guilt yourself” (Lev. 19:17). Correction respects the other’s dignity. It tells the truth so that the sinner can turn back. When he repents, you must forgive. Mercy is not a feeling you wait for; it is an obedience to God’s way of restoring communion.
Jesus presses the point with a hard example. If he wrongs you seven times in a day and returns seven times saying “I am sorry,” you must forgive. “Seven” signals fullness. In other words, disciples do not keep score. This does not erase justice or prudence; it ends the cycle of retaliation. Forgiveness keeps open the door to grace and reconciliation. Sirach warns that refusing mercy blocks our own prayer for mercy (Sir. 28:1-7). Jesus will teach us to pray “forgive us our sins, for we ourselves forgive everyone in debt to us” (Lk. 11:4). His command here embodies that same law of the kingdom.
The apostles hear this and know they are not strong enough. They ask, “Increase our faith.” Jesus answers with the mustard seed. Even faith as small as a seed can say to a deep-rooted tree, “Be uprooted and planted in the sea,” and it will obey. The point is not spectacle. The point is that authentic faith, though small, draws on God’s power. Forgiveness is often the hardest work we do. It feels impossible. But God can do this in us when we trust him and act on that trust. Taking the first obedient step—speaking the truth in charity, surrendering bitterness, praying for the offender—and letting God supply what we lack is mustard-seed faith.
There is a quiet order in these verses. Do not cause others to fall. When they fall, help them rise with honest, loving correction. When they turn back, restore them with real forgiveness—from the heart. Underneath it all is faith. We cannot live this way by willpower alone. We receive strength from the Lord who forgave his enemies from the Cross and whose Spirit heals our hearts. The Old Testament already pointed here: God casts our sins into the depths of the sea (Mic. 7:18-19). In Jesus, that promise becomes a lived pattern for his people.
This teaching also guards the Church’s witness. Scandal is speech or behavior that leads another to sin or makes sin seem acceptable. Causing scandal—treating sin as normal, inevitable, or admirable—breaks communion with God and discourages the weak. Honest rebuke without forgiveness becomes cold judgment. If we ‘forgive’ but refuse to name the wrong and tell the truth, we do not heal the wound; we avoid it. Jesus holds truth and mercy together in himself and commands us to do the same in our relationships.
In practice, this starts small. Refuse to pass along scandal by your words or example. If someone sins against you, seek the right moment and speak plainly without contempt. If he repents, forgive him and act accordingly. If the wound runs deep, bring it to prayer and ask for mustard-seed faith to take the next step—perhaps an act of blessing for the one who hurt you (cf. Lk. 6:27-36). The Lord who commands also supplies the grace.
Lord Jesus, give us the faith that acts on your word. Guard us from leading others into sin. Teach us to correct with charity and to forgive without counting, as you have forgiven us.
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Sources and References:
- Holy Bible, New American Bible, Revised Edition (NABRE), 2011 (Lk. 17:1-6; Lev. 19:17; Sir. 28:1-7; Mic. 7:18-19; Lk. 6:27-36; 11:4).
- Orchard, Bernard, et al. A Catholic Commentary on Holy Scripture. 1953.
- Faculty of the University of Navarre. The Navarre Bible: New Testament Expanded Edition. 2008.
- Chiu, José Enrique Aguilar, et al., eds. The Paulist Biblical Commentary. Paulist Press, 2018.
- Brown, Raymond E., et al., eds. The New Jerome Biblical Commentary. Prentice Hall, 1990
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