Mortification of sin is a duty always incumbent on us in the whole course of our obedience. This the command testifieth, which represents it as an always present duty. When it is no longer a duty to grow in grace, it is so not to mortify sin. No man under heaven can at any time say that he is exempted from this command, nor on any pretence; and he who ceaseth from this duty lets go all endeavours after holiness. And as for those who pretend unto an absolute perfection, they are of all persons living the most impudent, nor do they ever in this matter open their mouths but they give themselves the lie.
The Works of John Owen, 3:541.