Killing The Old Man

'To mortify. Ei thanatoute, -- "If you put to death;" a metaphorical expression, taken from the putting of any living thing to death. 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. It is, indeed, meritoriously, and by way of example, utterly mortified and slain by the cross of Christ; and the "old man" is thence said to be "crucified with Christ," Rom. vi. 6, and ourselves to be "dead" with him, verse 8, and really initially in regeneration, Rom. vi. 3-5, when a principle contrary to it, and destructive of it, Gal. v. 17, is planted in our hearts; but the whole work is by degrees to be carried on towards perfection all our days.'

--John Owen