It is our duty to mortify our members which incline to the things of the world. Mortify them, kill them, suppress them, as weeds or vermin which spread and destroy all about them. Continual opposition must be made to all corrupt workings, and no provision made for carnal indulgences. Occasions of sin must be avoided: the lusts of the flesh, and the love of the world; and covetousness, which is idolatry; love of present good, and of outward enjoyments. It is necessary to mortify sins, because if we do not kill them, they will kill us. The gospel changes the higher as well as the lower powers of the soul, and supports the rule of right reason and conscience, over appetite and passion.
– Matthew Henry’s Concise Commentary on Colossians 3:5-10