Matthew 18:6-9
6 But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea.
7 Woe unto the world because of offences! for it must needs be that offences come; but woe to that man by whom the offence cometh!
8 Wherefore if thy hand or thy foot offend thee, cut them off, and cast them from thee: it is better for thee to enter into life halt or maimed, rather than having two hands or two feet to be cast into everlasting fire.
9 And if thine eye offend thee, pluck it out, and cast it from thee: it is better for thee to enter into life with one eye, rather than having two eyes to be cast into hell fire.
The Grace New Testament Commentary - Matthew 18:6-9
18:6-7 Here Jesus is warning against causing "one of these little ones who believe in Me" to fall into sin (skandalizō, "to trip or cause to stumble"). There is something perverse about placing a stumbling stone in front of an unsuspecting or vulnerable child so they might fall. Those who do such things will face severe punishment. "It would be better" to have "a millstone" (a huge wheel-shaped stone used to grind grain) attached as a weight to one's body and sink quickly to the bottom "of the sea" than to commit such an offense.
Jesus is speaking here of children who believe in Him! Despite what some may suggest, believing in Jesus is not limited to adults. Children can and do believe in Him. God's judgment is expressed in Jesus' double use of the word woe. For the world, offenses are inevitable and so is the judgment against those who are responsible for them.
18:8-9 Jesus counsels the listeners to eliminate whatever "causes [them] to sin," whether a "hand or foot," or an eye. If one is in danger of going to hell because of what he might do, then he should cut off his feet and hands. If one is in danger of hell because of what he looks on, he should pluck out his eye. "To enter into life lame or maimed" is better than being "cast into hell fire" with one's whole body intact.
This enigmatic saying is hyperbolic and hypothetical. If drastic measures could be taken, such as dismemberment, to keep one from sinning, it would be worth it. Self-mutilation and dismemberment would not save them, of course, for the problem is in the heart (Matthew 15:8-9, 18-20). However, Jesus assumes for the sake of argument that their trust in external restraint from evil would be sufficient to save. The complete uselessness of such an exercise is plain. That they would trust in externals reveals that those to whom Jesus directs His remarks are unbelievers. Jesus' words are provocative and enigmatic, causing one to think and feel more deeply.
(Editor's note: Another view is that the Lord was suggesting that any hindrance to faith in Him should be eliminated. The hand, foot, and eye suggest what a person does, where he goes, and what he gazes on. While the only condition of eternal life is faith in Christ, a person who keeps himself away from the message about Jesus and is distracted by various friends and pursuits is unlikely to come to faith. Better to eliminate hindrances that keep one from hearing the saving message than to go through life with one's comfortable status quo and end up in hell.)