I think Jesus is explaining how sin works:
If your right eye causes you to sin, pluck it out and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell. And if your right hand causes you to sin, cut it off and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell. (Matt. 5:29,30)
Notice first it's the eye, then the hand, you look and then you reach. It reminds me of the progression in Psalm 1:
Blessed is the man that doth not walk in the counsel of the wicked, nor stand in the way of sinners, nor sit in the seat of the scornful. (Psalm 1:1)
Notice he is walking down the street, standing in the door way, then he is sitting down. You see this in the Sermon of the Mount in the immediate context. If you murder, you are subject to the judgment of a trial court, if your angry with your brother for no good reason you can be called before the council, Israel's highest court. If you call your brother a fool, your in danger of perdition, God's final judgment. See the progression?
Discipleship is from the inside out, it starts with what you look at with desire, dwell on, and finally seek to consummate.
You shall not covet your neighbor’s house. You shall not covet your neighbor’s wife, or his male or female servant, his ox or donkey, or anything that belongs to your neighbor. ( Exodus 20:17)
If your eye causes you to sin pluck it out, if your hand causes you to sin, cut it off. You may not have total control over every random desire but you definitely have a fair amount of control over what you gaze at longingly. In the Old Testament world the way wealth could be flaunted is to erect an idol of gold, the onlooker could even worship this inordinate display of wealth. Jesus is really saying be very careful what you set your heart on as you bring it in though the eye gate.
If ye then be risen with Christ, seek those things which are above, where Christ sitteth at the right hand of God. Set your affections on things which are above, and not on things which are on the earth. (Colossians 3:1-2)
If you do this you can avoid the trappings of idolatrous earthly affections (Colossians 3:5-6). And pursue the things of God (Colossians 3:12-16)
See how that works?
Grace and peace,
Mark