What does Matthew mean by "if your eye causes you to sin, tear it out", etc.?

In Matthew chapter 18 Jesus is covering Salvation and what it means and giving tips on how to live the Christian life.

In verse 9 did Jesus mean to physically gouge out your eyes? Probably not any more than when he told Nicodemus that he must be born again did mean to physically go back into the womb and start all over.

In both these incidents Jesus was referring not to a physical process, but a spiritual process.

consider:

Matthew 5:27 and 28 KJV

27 Ye have heard that it was said by them of old time, Thou shalt not commit adultery:

28 But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart.

What would seem more feasible is that Jesus was saying wickedness is not confined to actions, but that we must also clean up our minds. And in order to do that it is not going to be easy. Remember the old saying that it will cost an arm and a leg. The meaning there was that it was going to be really expensive, and in verse nine the connotation is probably similar.

Matthew 18:3-9 (DRB)

3 And [Jesus] said: Amen I say to you, unless you be converted, and become as little children, you shall not enter into the kingdom of heaven. 4 Whosoever therefore shall humble himself as this little child, he is the greater in the kingdom of heaven. 5 And he that shall receive one such little child in my name, receiveth me. 6 But he that shall scandalize one of these little ones that believe in me, it were better for him that a millstone should be hanged about his neck, and that he should be drowned in the depth of the sea. 7 Woe to the world because of scandals. For it must needs be that scandals come: but nevertheless woe to that man by whom the scandal cometh. 8 And if thy hand, or thy foot scandalize thee, cut it off, and cast it from thee. It is better for thee to go into life maimed or lame, than having two hands or two feet, to be cast into everlasting fire. 9 And if thy eye scandalize thee, pluck it out, and cast it from thee. It is better for thee having one eye to enter into life, than having two eyes to be cast into hell fire.

The argument is quite simple (and very obviously not about literal mutilation—and was never understood that way):

• Occasion (or, cause) of sin: in this instance, an intrument of temptation. Such must, necessarily be avoided, because sinning by them, you will lead yourself to Hell.

• Punishment for letting an occasion of sin remain: in this instance, the Hell to which the sins committed due to said temptations or occasions of sin leads the sinner.

He doesn't mean (in my view) we will be in heaven nor hell maimed, necessarily: the teaching is hyperbolic. He is bringing to focus the cost of sin.

What is certainly not hyperbolic and the lowest common denominator of what He is trying to teach is that sin, if we do not avoid and make efforts to avoid it (removing occasions of sin, for example), will certainly lead us to Hell—the "than"s separate the only two options: Heaven or Hell. He even teaches the same thing twice with more examples, to drive the point through (with parallelism accounting for the two names for Hell: "hell of fire ['Gehenna']" and "everlasting fire").

This is what St. Paul refers to when he writes about putting to death the deeds of the flesh, otherwise "ye shall die:"

Romans 8:13 (DRB)

For if you live according to the flesh, you shall die: but if by the Spirit you mortify the deeds of the flesh, you shall live.

This is Jesus' characteristically hyperbolic teaching unpacked by St. Paul.

I could literally mean “And if your eye causes you to sin, tear it out and throw it away. It is better for you to enter life with one eye than with two eyes to be thrown into the hell of fire.”

That's fairly straightforward. Eternal intense, unimaginable, agonizing suffering, or temporary pain and blindness... The choice is yours.

Kind of puts the real requirements for goodness and holiness required of us by God into perspective. We all think "We're not so bad", but if you ever get a real understanding of God's requirements, you realize that there's no way we can attain to that level of perfection. None of us is good enough to get to heaven. Thankfully, He provided the lamb of God to pay the penalty for our sins, since we can't.

However, it is typically used as a hyperbole to make a principle clear:

If you have things in your lift that are causing you to sin, get rid of them. It's better to have temporary loss in this world than eternal loss. Love the things of God, and get rid of those things that are not Godly, that cause you to stumble.

Companion verse: John 12:25.

If your eye causes you to sin, tear it out means that we have to avoid all the conditions in our human body which leads to doing sins. When we read the scriptures, do not take it's physical meaning try to understand the spiritual meaning which is not visible directly to our brain. Our body parts are leading us to do sins so we have to control the organs under divinity. That is the meaning.