Romans 8:13

13.For if ye will live after the flesh, etc. He adds a threatening, in order more effectually to shake off their torpor; by which also they are fully confuted who boast of justification by faith without the Spirit of Christ, though they are more than sufficiently convicted by their own conscience; for there is no confidence in God, where there is no love of righteousness. It is indeed true, that we are justified in Christ through the mercy of God alone; but it is equally true and certain, that all who are justified are called by the Lord, that they may live worthy of their vocation. Let then the faithful learn to embrace him, not only for justification, but also for sanctification, as he has been given to us for both these purposes, lest they rend him asunder by their mutilated faith.

But if ye by the Spirit, etc. He thus moderates his address, that he might not deject the minds of the godly, who are still conscious of much infirmity; for however we may as yet be exposed to sins, he nevertheless promises life to us, provided we strive to mortify the flesh: for he does not strictly require the destruction of the flesh, but only bids us to make every exertion to subdue its lusts.