For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live.
(Romans 8:13)
Some animals cannot be tamed. You may call a snake your pet and give it a cute name, but that doesn’t take the wild out of it. No matter how long you’ve housed, cared for, and fed a boa constrictor, it may still turn on you. After all, it is still a snake.
It is much the same with sin. You may cuddle sin like a pet, but that doesn’t take the wild out of it or make it less dangerous. Evil cannot be domesticated. Sin is poised to attack your faith at any moment. Sometimes it bares its fangs and strikes in a surprise attack. Sometimes it is cunning enough to play dead and subtle enough to pose as something good. But either way, sin is wired to kill. Slowly, cleverly, when you’re not paying attention, sin will squeeze the faith, love, and holiness right out of you…
Think for a moment about the act of killing. How do you kill something? To make this more palatable, let’s consider snakes again! There are lots of ways to kill a snake. You can crush it with a rock, starve it, burn it, drown it, or chop off its hideous little head. Choose your favorite method, but what you’re essentially doing in each is depriving the snake of something it needs to live—be it brains, food, air, or a hospitable environment. That’s what we have to do with sin in the heart. We have to weakensin by taking away the things that give it strength, by depriving it of food and air, as it were. This means that one of the most practical ways to kill sin is to quit giving it opportunities to thrive: “Make no provision for the flesh, to gratify its desires” (Romans 13:14b). Or in the words of seventeenth-century pastor John Owen, “Be killing sin or it will be killing you.”
—Brian Hedges, Licensed to Kill: A Field Manual for Mortifying Sin, 7-8. (HT: BT)