To kill a man, or any other living thing, is to take away the principle of all his strength, vigour, and power, so that he cannot act or exert, or put forth any proper actings of his own; so it is in this case. Indwelling sin is compared to a person, a living person, called "the old man," with his faculties, and properties, his wisdom, craft, subtlety, strength; this, says the apostle, must be killed, put to death, mortified, -- that is, have its power, life, vigour, and strength, to produce its effects, taken away by the Spirit.