The Soul and Substance of All False Religion

The principal efficient cause of the performance of this duty is the Spirit mentioned (v. 11), the 'Spirit of Christ', the Spirit of God that dwells in us (v.9), that quickens us (v.11), the 'Spirit of adoption' (v.15), the Spirit that maketh intercession for us (v.26). All other ways of mortification are vain; all helps leave us helpless; it must be done by the Spirit. Men, as the apostle intimates (Rom. 9:30-32), may attempt this work on other principles, by means and advantages administered on other accounts, as they always have done and do: but (saith he) this is the work of the Spirit; by him alone it is to be wrought, and by no other power is it to be brought about. Mortification from a self-strength, carried on by ways of self-invention, unto the end of a self-righteousness, is the soul and substance of all false religion in the world.

-John Owen, from The Mortification of Sin, on Romans 8:13