Adam Clarke on Romans 8:13

For if ye live after the flesh, ye shall die - Though μελλετε αποθνησκειν may mean, ye shall afterwards die, and this seems to indicate a temporal death, yet not exclusively of an eternal death; for both, and especially the latter, are necessarily implied.

But if ye through the Spirit - If ye seek that grace and spiritual help which the Gospel of Christ furnishes, resist, and, by resisting, mortify the deeds of the flesh, against which the law gave you no assistance, ye shall live a life of faith, love, and holy obedience here, and a life of glory hereafter.