In his chapter, “The Necessity of Mortification” in his book, Of the Mortification of Sin in Believers, John Owen gives us a few summary principles, from his exegetical musings on Romans 8:13:
The choicest believers, who are assuredly freed from the condemning power of sin, ought yet to make it their business all their days to mortify the indwelling power of sin (47).
The mortification of indwelling sin remaining in our mortal bodies, that it may not have life and power to bring forth the works or deeds of the flesh, is the constant duty of believers.(49).
The vigor, and power, and comfort of our spiritual life depends on the mortification of the deeds of the flesh (49).
Do you mortify; do you make it your daily work; be always at it while you live; cease not a day from this work; be killing sin or it will be killing you (50).
When sin lets us alone we may let sin alone; but as sin is never less quiet than when it seems to be most quiet, and its waters are for the most part deep when they are still, so ought our contrivances against it to be vigourous at all times ad in all conditions, even where there is least suspicion (51).
If sin be subtle, watchful, strong, and always at work in the business of killing our souls, and we be slothful, negligent, foolish, in proceding to the ruin thereof, can we expect a comfortable event? There is not a day but sin foils or is foiled, prevails or is prevailed on; and it will be so while we lie in this world (52).
