Because of his spirit, etc. There are different readings of this final clause. Soden prefers the genitive reading: “through the Spirit dwelling in you,” which would mean that the Holy Ghost will be the immediate cause of our resurrection. The accusative reading, which is that of the oldest MSS., has: δια το ενοικουν αυτου πνευμα, i.e., “on account of the Spirit dwelling in you,” propter dignitatem Spiritus, etc. This latter is the reading adopted in the Vulgate.
Rom 8:12 Therefore, brethren, we are debtors, not to the flesh, to live according to the flesh.
Rom 8:13 For if you live according to the flesh, you shall die: but if by the Spirit you mortify the deeds of the flesh, you shall live.
These two verses are a corollary from all that has been said since chapter 6, and they give the final answer to the objections of Rom 6:1 and Rom 6:15. From what has been said it follows that for all the benefits that have been enumerated we are not debtors to the flesh, which enslaved us to sin and which of itself would again reduce us to slavery. The Apostle leaves it to be understood that we are debtors to the Spirit, to live according to Its dictates rather than according to the dictates of the flesh.
The works of the flesh lead to the death of the soul here and hereafter. But if we live in the spirit which we have received in Baptism, which is a principle of spiritual life in us, opposing to the works of the flesh the works of grace, we shall live now the life of grace, and hereafter the life of glory. There are, therefore, for the Christian the alternatives of eternal life, if he lives according to the spirit; or of eternal death, if he follows the dictates of the flesh. The spirit here means the principle of the spiritual life, namely, grace (Cornely), and not the Holy Ghost (Zahn, Kuhl). With this verse St. Paul has done with the flesh, and turns to consider more exclusively the spirit.