Galatians 5:16 does not teach that believers are sanctified by choosing to obey the command to walk in the Spirit. Believers lack any inherent spiritual power to produce holiness or conquer sin.
Believers stand in constant need of the actual aid of the Holy Spirit for every act of obedience. The command to "walk" does not imply human self-sufficiency; rather, it is a summons to rely on God's active, internal provision. The Holy Spirit is the ultimate agent who mortifies the flesh and bears fruit in the Christian.
Romans 8:2 teaches that believers are permanently freed from the penalty and ruling power of sin and death, but not yet free from the presence of daily sin. Romans 8:2 flows directly from 8:1 ("there is therefore now no condemnation").
Believers are legally and eternally freed from the guilt of sin and the ultimate punishment of spiritual death.
As seen in Romans 7, indwelling sin remains in the Christian. Believers are still overcome by temptation and commit sins daily, in a lifelong war against the flesh.
So Romans 7 describes the reality of being overwhelmed by temptation everyday. While Romans 8 declares that believers are forgiven for all of our past, present and future sins. So we don't need to fear any judgement or punishment. That's the good news, which is cause for great joy.
Nobody claimed that sin was David's or Pauls master, the claim is that we can rejoice in the knowledge that Christ has already paid for every sin so none of us will be punished for them. If you're at war with the enemy, then the enemy is not your master. The enemy can only be your master if they have the final victory.
You never have the final victory in this life, because it's impossible. Your enemy is infinitely more powerful than you are so you have no chance of victory against the enemy.
The exhortation in Romans 8 is to fight, it's not to give you false hope of some non existent victory against the flesh.
You're creating a contrast that Paul himself does not make.
Romans 8 does not merely say believers are forgiven while remaining perpetually overwhelmed by sin.
It says, "the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death" (Rom. 8:2), and "if ye through the Spirit do mortify the deeds of the body, ye shall live" (Rom. 8:13).
Those are not descriptions of an inevitable, daily defeat with no expectation of actual victory.
The problem is that your conclusion goes beyond saying believers still sin.
We all agree they do.
Your conclusion is that victory over the flesh in this life is essentially nonexistent.
Yet Paul says, "walk in the Spirit, and ye shall not fulfil the lust of the flesh" (Gal. 5:16).
He does not say, "walk in the Spirit and you will still inevitably be overwhelmed every day."
The command assumes the Spirit produces a real effect.
Likewise, Romans 6 does more than promise future forgiveness.
Paul repeatedly says believers are dead to sin, freed from sin, no longer servants of sin, and that sin shall not have dominion over them (Rom. 6:2, 6, 7, 14, 18, 22).
If all of those statements merely mean "you won't be punished later," then Paul's argument loses much of its force.
He is describing something God has already accomplished in the believer's present relationship to sin.
I agree completely that believers have no inherent power in themselves.
Any obedience, victory, or holiness comes from the Holy Spirit.
But that is precisely the point.
The Spirit's work is not limited to assuring us that future punishment is removed.
The Spirit actively produces righteousness, mortifies the deeds of the body, and bears fruit in the believer's life.
No one is claiming sinless perfection.
Scripture expressly teaches an ongoing conflict between flesh and Spirit.
But conflict is not the same thing as continual defeat, and warfare is not the same thing as being overwhelmed every day.
Paul's message is not, "Fight a battle you cannot win."
His message is that through the Spirit, sin is no longer the reigning master.
The believer stumbles, falls, repents, and continues the fight, but Scripture never presents the normal Christian life as one of unavoidable bondage with no meaningful victory until glorification.
Romans 6 and 8 say exactly the opposite.
