Mark 9:42-50
42 And whosoever shall offend one of these little ones that believe in me, it is better for him that a millstone were hanged about his neck, and he were cast into the sea.
43 And if thy hand offend thee, cut it off: it is better for thee to enter into life maimed, than having two hands to go into hell, into the fire that never shall be quenched:
44 Where their worm dieth not, and the fire is not quenched.
45 And if thy foot offend thee, cut it off: it is better for thee to enter halt into life, than having two feet to be cast into hell, into the fire that never shall be quenched:
46 Where their worm dieth not, and the fire is not quenched.
47 And if thine eye offend thee, pluck it out: it is better for thee to enter into the kingdom of God with one eye, than having two eyes to be cast into hell fire:
48 Where their worm dieth not, and the fire is not quenched.
49 For every one shall be salted with fire, and every sacrifice shall be salted with salt.
50 Salt is good: but if the salt have lost his saltness, wherewith will ye season it? Have salt in yourselves, and have peace one with another.
The Grace New Testament Commentary - Mark 9:42-50
9:42 In contrast, "whoever causes one of these little ones who believe in Me to stumble" will be punished. The fact that Jesus speaks of little ones who believe in Me means that children can indeed believe in Him for everlasting life. These little ones lived in the unbelieving culture of Judaism and were easy prey for the false teaching of the religious leaders (cf. Mark 8:15). His warning to the offender that "it would be better for him if a millstone" (a large millstone required a donkey's strength to move) "were hung around his neck and he were thrown into the sea" is deadly, temporal judgment.
9:43-48 Many things may hinder one from believing in Christ. Hand (v 43), foot (v 45), and eye (v 47) refer to things one handles, places he goes, or things he sees that can cause him to stumble (cf. vv 43, 45, 47). Therefore Jesus commands to cut it off (hand or foot, vv 43, 45) or pluck it out (eye, v 47). Jesus is using hyperbole to make the point that drastic measures are sometimes required to remove hindrances to faith from an unbeliever's life. Belonging to an unbelieving religious group, reading heretical books, attending a liberal, unbelieving school, or having close friends who are unbelievers, all can hinder faith in Christ.
To turn from such hindrances may be painful, but Jesus reasons that "it is better for you to enter into life maimed, rather than having two hands (feet, eyes) to go to hell." It is better to believe in Jesus having cut out of one's life things that a person once enjoyed, than to keep those things but never believe in Jesus. Hell (gehenna) is described as "the fire that shall never be quenched" (lit., "inextinguishable") with the quotation from Isa 66:24 (Mark 9:44, 46, 48) that the "worm does not die" and the "fire is not quenched". Gehenna was a valley outside Jerusalem which became a garbage and sewage dump where fire and worms continually consumed the trash.
9:49 "For everyone will be seasoned (lit., "salted") with fire" explains the previous warning. While unbelievers will end in hell fire, everyone (including believers) will be salted with fire. Salt symbolized the covenant of God to Israel, and their offerings were to be presented literally with this in mind (cf. Lev 2:13). As OT sacrifices were salted before they were presented to God, believers will be salted with fire. This phrase suggests that figurative speech is being used for trials (cf. 1 Pet 1:7; 4:12).
Also the phrase "every sacrifice will be seasoned with salt" (lit., "with salt will be salted") adds another element to the sufferings of believers. As Christ will soon give His life as a sacrifice, so every believer is called to live as a sacrifice to God (cf. Mark 8:34; Rom 12:1; Phil 4:18; Heb 13:15-16: 1 Pet 2:5), knowing that suffering precedes glory. Another view is that this anticipates the judgment of all people. Unbelievers will be "salted" with hell fire while believers will be "salted" with fire at the Judgment Seat of Christ (cf. 1 Cor 3:13, 15: 2 Cor 5:9-11). However, this mixes metaphors as the fire of hell is literal, whereas the fire at the Judgment Seat is figurative.
9:50 Salt was good in Palestine for preservation, seasoning, medicinal uses, and, along with wine and oil, for sustaining life. The command "Have salt in yourselves and have peace with one another" signifies that believers need to be useful in promoting peace with fellow disciples, especially with those who may not be in their group (cf. Mark 9:38-40). Peace and love among believers are essential elements in being salt in the world (cf. John 13:35; 14:27).
Charles Bing - Grace, Salvation, and Discipleship - Plucking Out Your Eye, Matthew 5:29-30 (cf. Mark 9:43-48)
(Salvation) Interpretation: A person who does not do what is necessary to stop sinning will be thrown into hell.
(Discipleship) Interpretation: It is better to be a believer who suffers loss in order to stop sinning than to be a whole unbeliever thrown into hell.
We remember that Jesus is addressing His disciples with the multitude listening in. He is not telling His disciples that if they continue to sin they will lose their salvation. He is certainly not suggesting if people stop sinning they will avoid hell. He is telling his disciples that kingdom conduct demands a radical effort to avoid a serious sin like the sin of adultery that He mentions (vv. 27-28). Of course, plucking out the eye and cutting off the hand are metaphors for a radical commitment to not sin. While the disciple will have to suffer severely in order to deny his sinful desires, he is better off than an unsaved person who sins with abandon, makes no effort to avoid sin, and remains a whole person (with all his body parts), but is thrown into hell. While cutting off body parts is symbolic, the reality behind the metaphor can involve things like suffering a financial loss to avoid sin, suffering a severed relationship, or suffering a relocation to avoid a temptation. The loss is real and may be painful, but it is nothing compared to those who refuse to deal with their sin and end up in hell.
Mark 9:43-48 uses the same metaphors (but includes cutting off a foot) and the same consequences. In this context, Jesus is teaching his disciples a lesson about greatness in the anticipated kingdom (Mark 9:33-35). Greatness is found in those disciples who value, accept, and serve those who are younger, weaker, and less committed to Christ (the children of Mark 9:36-37 and the one who is not following Christ as a committed disciple, vv. 38-41). Together, these are the "little ones" or the young and immature believers of verse 42. It is a serious offense to the Lord to cause one of these to sin, and therefore wreck their fragile faith, as is shown by the reference to hanging a millstone around the offender's neck and throwing him into the sea.
In verse 43, there is a dramatic shift from talking about someone who causes a little one to sin to directly addressing the disciples' potential to sin. This is probably because a disciple who sins can lead a less mature believer to sin also. As disciples, suffering a temporary loss (if we continue with the metaphor, all body parts would be restored in eternity) and entering life is a better fate than an unbeliever who suffers no loss as he indulges in sin and goes to hell with all his body parts, a whole person (vv. 43-48). Disciples shouldn't grieve about losses in this life when they sacrifice desires for the sake of others, because enduring such a brief loss is nothing compared to the fate of an unbeliever. Worse, the sin of an indulgent unbeliever may cause a little one to sin, bringing the severe punishment represented by the millstone and watery fate.
As followers of Christ, we have a kingdom responsibility to take drastic measures to avoid sin. Sin misrepresents the Lord, despises His grace, and can cause less mature believers to sin, injuring their walk with the Lord. The Lord takes sin seriously, and so should we.