Sanctify means to set apart, declare holy, consecrate, purify, and to separate from sin.
1 John 2:15-17,
"15 Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him.
16 For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world.
17 And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever." (KJV)
God wants us to walk in the Spirit, and not the flesh.
"There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
5 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit." (KJV)
So, we are called to seek after Christ, and to walk in the Spirit. Our salvation is conditional, in that we must continue to walk with Him, and abide in His ways. If we turn our back on Him, and go back to a sinful life, then we will lose our promise of inheritance. Compare it to a father's will which promises a son will inherit all that His father has with certain stipulations. Salvation is not unconditional (2 Pet. 1:10-11; John 15:6; Rom. 11:21-22).
Therefore, we have to overcome the fleshly desires. The flesh does not inherit eternal life. 1 Cor. 15:50,
"Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; nor does corruption inherit incorruption." (NKJV)
Finishing Romans 7:23-25,
" But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. 24 O wretched man that I am! Who will deliver me from this body of death? 25 I thank God—through Jesus Christ our Lord! So then, with the mind I myself serve the law of God, but with the flesh the law of sin." (NKJV)
We have a constant battle between our selfish desires which benefit the flesh (e.g., power, money, sex, material goods, etc.) and the spiritual recognition of abiding by the law of Christ.
When we are in Christ, we have the promise of remission of sins as we repent of them (Acts 2:38; 10:43; Heb. 6:6). This promise keeps washing us throughout our lives, and is purifying us from sins as we repent of them.
Christ said in Matt. 22:36 -40,
"“‘You shall love the Lord your God with all your heart, with all your soul, and with all your mind.’[d] 38 This is the first and great commandment. 39 And the second is like it: ‘You shall love your neighbor as yourself.’[e] 40 On these two commandments hang all the Law and the Prophets.”" (NKJV)
Many times our selfish desires do not comport with the needs of others, nor with loving YHWH before ourselves. It is the growing up process, maturing in the spirit from the stage of children who want whatever they see and the mature adult who recognizes that we sacrifice our desires to give to others.
So our fleshly desires and wants must be under control of our mind and heart that is joined in spirit with Christ. And, if we are in Christ, then He has set us apart for Him, and we are living sacrifices for Him. He will purify our souls when we ask for forgiveness, if we have repented. The purification is not of the flesh.
When we fall, then we need to repent from our sins, and ask His forgiveness. We pick ourselves back up and continue to fight that battle between our fleshly desires and the gospel of Christ.
1 Cor. 9:24-27,
"24 Do you not know that those who run in a race all run, but one receives the prize? Run in such a way that you may obtain it. 25 And everyone who competes for the prize is temperate in all things. Now they do it to obtain a perishable crown, but we for an imperishable crown. 26 Therefore I run thus: not with uncertainty. Thus I fight: not as one who beats the air. 27 But I discipline my body and bring it into subjection, lest, when I have preached to others, I myself should become disqualified." (NKJV)
It is a race against sin, that we live with day in and day out. If we are able to stay in Christ, to repent and ask for His forgiveness when we fall, to keep running that race, then when we die in the Lord, we will receive the crown.
Our inheritance is in heaven above. So, He does not need to sanctify the flesh as only the spirit inherits eternal life.
1 Cor. 15:53,
" For this corruptible must put on incorruption, and this mortal must put on immortality. " (NKJV)