Romans 8:13

For if ye live after the flesh, ye shall die--in the sense of Rom 6:21. but if ye through the Spirit do mortify the deeds of the body--(See on Rom 7:23). ye shall live--in the sense of Rom 6:22. The apostle is not satisfied with assuring them that they are under no obligations to the flesh, to hearken to its suggestions, without reminding them where it will end if they do; and he uses the word "mortify" (put to death) as a kind of play upon the word "die" just before. "If ye do not kill sin, it will kill you." But he tempers this by the bright alternative, that if they do, through the Spirit, mortify the deeds of the body, such a course will infallibly terminate in "life" everlasting. And this leads the apostle into a new line of thought, opening into his final subject, the "glory" awaiting the justified believer. Note, (1) "There can be no safety, no holiness, no happiness, to those who are out of Christ: No "safety," because all such are under the condemnation of the law (Rom 8:1); no holiness, because such only as are united to Christ have the spirit of Christ (Rom 8:9); no happiness, because to be "carnally minded is death" (Rom 8:6)" [HODGE]. (2) The sanctification of believers, as it has its whole foundation in the atoning death, so it has its living spring in the indwelling of the Spirit of Christ (Rom 8:2-4).

— Jamieson-Fausset-Brown Commentary (public domain)