13 For if you live according to the flesh [according to the dictates of the sin capacity] you will die; but if by the Spirit you put to death the deeds of the body, you will live.
The word “for” here is an explanation of verse 12. Liberation from ultimate death in eternity does not liberate us from dealing with the flesh in time.
if you live [present tense, continue to live] according to the flesh
The “if” (since) here indicates reality. It is a reality that if we succumb to the standards of the flesh we will die.
The switch to “you” from “we” indicates the real dangers of living according to the norm of the flesh. The “you” here are believers. If believers live with their horizons bound by the flesh, this is death.
Living here has to do with the Spirit-filled life, not salvation, and death is spiritual failure. Non-believers are already dead in trespasses and sin. A believer cannot lose his or her salvation:
Ro 8:38-39, For I am persuaded that neither death nor life, nor angels nor principalities nor powers, nor things present nor things to come,39 nor height nor depth, nor any other created thing, shall be able to separate us from the love of God which is in Christ Jesus our Lord.
Both life and death have two meanings:
Eternal life and spiritual life in time
Eternal death and spiritual death in time
you will [as a consequence] die [temporally];
The Greek indicates that the phrase “will die” is about to die, indicating the certainty of the corrupting process of the flesh. The issue is a pressing one. This is the death of spiritual living. This kind of death is inevitable for those out of fellowship with God. As long as we continue in unconfessed sin, God will separate Himself from fellowship with us. The essential idea of death is separation. The subject here is not eternal death in hell but the death of the spiritual life. If we live according to the flesh we are on the point of dying spiritually in time. God does not view those walking in the flesh as dead but about to die spiritually.
“Die” here is dying to God. It is not possible to have fellowship with God if we live according to the standards of the flesh. This cannot be physical death because that is inevitable in any case.
Clearly, the believer is in view in this passage (Ro 8:12). The plural “you” here harks back to “brethren” in verse 12. It is possible for the truly regenerate to live according to the flesh (Ro 7:7-24; 8:1-12). In none of those passages will a believer forfeit eternal life if he lives according to the flesh; in fact, the opposite is stated in 8:1: “There is therefore now no condemnation to them who are in Christ Jesus.” The present tense “putting to death” involves ongoing struggle with sin and not with an event. Thus, the putting to death here is temporal rather than eternal.
The Bible presents various forms of death, not just eternal death in hell. Christians face physical death when they sin (1 Co 11:30; 1 Jn 5:16; Jas 5:19-20). Christians face temporal death in their fellowship with God when they sin (Ep 5:14).
To make death here refer to the second death in hell would violate everything the Spirit has argued to this point in the epistle. God does not give temporal life but eternal life at salvation.
God warns believers with a great red light that living under the sin capacity will result in time-based death of our spiritual lives.
Those of us who choose to walk by the sin capacity are on a fatal course of our spiritual lives in time. Although God addresses us as His people, we can still walk according to the norms of the flesh. This involves rejection of walking in the Spirit.
Many Christians need to awaken from temporal spiritual death.
Eph 5:14, Therefore He says: “Awake, you who sleep, Arise from the dead, And Christ will give you light.”