28 But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart. 29 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. (Matthew 5:28–29, NKJV)
Jesus said the place sin begins is the heart. The heart is the mind, the seat of our intellect, will, emotions, conscience, and volition. “Lust” means to “set the heart upon,” to “long for” (Strong’s Concise Dictionary of Greek NT Words, I:31). In the heart, lusts (and plans to fulfill them) are contemplated, formulated, and postulated before they are practiced (Jas. 1:14-15). The mind is also the place where lusts can be regulated, resisted and refused (Jas. 1:16; 1 Cor. 10:13). Jesus used exaggerated language in vss. 29-30 to describe the extent of the repentance required to remove the source of sin and escape the suffering of hell. Repentance changes the heart so that the lust to sin no longer has a place to reside within us. To repent of our sins we will have to surrender things very dear to us in order not to perish in sin. (The removal of an eye or a hand illustrates the severe nature of repentance.) We will not see the profit of severing our connection to the sin in our hearts as long as our lusts are more precious to us than eternal life. Giving up sin is a small price to pay to escape the everlasting punishment of hell.