8:13 {15} For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live.
(15) Another reason for the profit that follows: for those who battle and fight valiantly will have everlasting life.
8:13 But if ye through the Spirit. By following the Spirit, minding the things of the Spirit (Ro 8:5), we secure life. This is shown in Ro 8:11.
The deeds of the body are the sinful deeds suggested by the fleshly desires. We cannot in our own strength mortify, i.e. put an end to, the deeds of the body. It is accomplished by the aid of the Spirit, helping our spirit in the effort.
8:13 The deeds of the flesh - Not only evil actions, but evil desires, tempers, thoughts. If ye mortify - Kill, destroy these. Ye shall live - The life of faith more abundantly here, and hereafter the life of glory.
8:10-17 If the Spirit be in us, Christ is in us. He dwells in the heart by faith. Grace in the soul is its new nature; the soul is alive to God, and has begun its holy happiness which shall endure for ever. The righteousness of Christ imputed, secures the soul, the better part, from death. From hence we see how much it is our duty to walk, not after the flesh, but after the Spirit. If any habitually live according to corrupt lustings, they will certainly perish in their sins, whatever they profess. And what can a worldly life present, worthy for a moment to be put against this noble prize of our high calling? Let us then, by the Spirit, endeavour more and more to mortify the flesh. Regeneration by the Holy Spirit brings a new and Divine life to the soul, though in a feeble state. And the sons of God have the Spirit to work in them the disposition of children; they have not the spirit of bondage, which the Old Testament church was under, through the darkness of that dispensation. The Spirit of adoption was not then plentifully poured out. Also it refers to that spirit of bondage, under which many saints were at their conversion. Many speak peace to themselves, to whom God does not speak peace. But those who are sanctified, have God's Spirit witnessing with their spirits, in and by his speaking peace to the soul. Though we may now seem to be losers for Christ, we shall not, we cannot, be losers by him in the end.