Mark 9:45, commentary and pictures

The foot stands for anything that leads into sin or causes stumbling, and cutting it off expresses how seriously such a cause must be removed whatever the sacrifice. This includes harshness or coldness by a disciple toward someone Christ is drawing, which can stumble that person and contribute to the loss of a soul. The things to be cut off include envy, malice, evil thinking, evil speaking, and covetousness, as weights to be laid aside in the race for immortality. Even one cherished sin degrades character, misleads others, and violates the eternal principles of right so that the blessing of heaven cannot attend.

Removal must be decisive and at any personal cost, rather than cherishing what leads to sin. As a hand or foot would be cut off or an eye plucked out to save the body from death, so the Christian must be still more earnest to put away sin because sin brings death to the soul. Clinging to self and refusing God's will is choosing death. Entering into life is better than being cast with two feet into hell, and life is received from God as the fountain of life through communion with Him and surrender of the will. Sin may be hidden from people but not from God, whose presence consumes sin so that those who refuse to separate from sin are consumed with it.

The fire that never shall be quenched is the sure experience and destruction of everyone who persists in sin by refusing Christ, forgiveness, grace, and entire obedience to God's law, remaining separated from God under His wrath. By it every unrepentant sinner will have soul and body destroyed. That unquenchable fire means remorse, despair, hatred, and bitterness against God when punished for transgression, with the too-late realization that sin is the transgression of God's law, that the soul is cut off from God, and that God's wrath abides upon him. The verse's Gehenna presents an image of a place of torment and horror, like foul, suffocating air in a crowded railroad car.