1 Peter 3:18 - Christ also suffered for sins once, the righteous for the unrighteous, that he might bring you to God; being put to death in the flesh, but made alive in the spirit. -- Young’s Literal.
Romans 8:8 Those who are in the flesh can't please God.
Romans 8:9 But you are not in the flesh but in the Spirit, if it is so that the Spirit of God dwells in you. But if any man doesn't have the Spirit of Christ, he is not his.
The claim is sometimes made that "in the flesh" and "in the spirit" of 1 Peter 3:18 contrasts the fleshly, carnal, or sinful way of life with that of the spiritual, godly way of life. Romans 8:8,9 is referred to as support of this.
Peter states regarding Jesus’ sacrifice that Jesus suffered for sins once, in that he was put to death in the flesh. If the thought is to apply Romans 8:8,9 to what Peter stated in 1 Peter 3:18, the logical conclusion would be that the sacrifice that Jesus gave for sin was was that he died toward walking in the sinful flesh. (Romans 8:3) However, as was stated, Jesus’ flesh was not sinful. Peter said that Jesus was righteous, that is, he was not of the crooked, unrighteous, generation that has come through Adam. -- Genesis 3:17-20; Ecclesiastes 1:2,13-15; 7:13; Romans 5:12-19; 8:20-22; Philippians 2:15.
This is supported by what Peter had stated earlier in that same letter (1 Peter 1:18,19):
You were redeemed, not with corruptible things, with silver or gold, from the useless way of life handed down from your fathers, but with precious blood, as of a lamb without spot, the blood of Christ.
Peter is indeed talking about the actual sacrifice of Jesus’ flesh with its blood.
Romans 8:8,9 refers to walking in accordance with the sinful flesh versus walking in accordance with the spirit. It is contrasting the new creation in Christ with the old creation, the sons of disobedience. Jesus’ flesh, of course, was not sinful, although he came in the likeness of sinful flesh and, although he suffered as though he were a sinner, he proved that a sinless man can be remain obedient, by which obedience he condemned sin in the flesh. Jesus’ obedience, in itself, was the sacrifice that Peter wrote of in 1 Peter 3:18.
It says nothing about being either a spirit being or a human being. The son of God are first reckoned, not as having spiritual bodies, but as having bodies of flesh. Jesus’ sacrifice only restores man to what Adam lost; Adam did not lose a celestial, spiritual body; he lost a terrestrial, earthly, physical body. When Adam disobeyed, all of his offspring are counted in God’s sight in that disobedience. It would take another man, having a sinless body of flesh as Adam possessed before Adam sinned, a man outside of the condemnation in Adam, who could offset the condemnation of the human race that has about by mean’s Adam’s disobedience.
Raised in the Spirit
Jesus Died a Human Being, Raised a Spirit Being
The Manner of the Resurrection
In Romans 8, it speaks of these as the sons of God; these sons of God were once of those sons of disobedience (Ephesians 2:1-10), but they are made alive (reckoned / counted / imputed / considered [Strong’s #3049] justified and as alive -- Romans 4:3-24; 6:11) as new creatures [sons of God] in Christ (Romans 8:16,19) through faith in Jesus. (Galatian 3:26) Jesus, however, was never such a son of disobedience; his birth into this world was not under the condemnation of Adam, since it was God who had especially prepared Jesus’ body of flesh. (Matthew 1:20; Hebrews 10:5)
Those who walk after the flesh have their minds set on things of the flesh – the things seen; those regenerated as sons of God are to walk after the spirit and to have their minds set on the things of the spirit — that which is not visible, but seen by the eye of faith. The regenerated son of God is walking in the spirit, not walking in the sinful flesh, as the apostles says, “if the spirit [mind, disposition] of God dwells in [stays within] you,” in contradistinction to living to the flesh, and having sin dwelling in us. (Romans 7:17,20) The disposition (spirit) of Christ in the believer would mean that they would be following the likeness of the spirit that he has, as sons of God.
Jesus’ sacrifice was not that he stopped walking in the sinful flesh, for his flesh was never sinful, although he did take upon himself the likeness of sinful flesh, in that he suffered to pay the wages of sin as though he were a sinner. If Jesus’ sacrifice was that he stopped walking in the sinful flesh, that would mean that his flesh was sinful, and such a sacrifice would have been meaningless to pay the wages of sin. -- 1 Corinthians 15:21,22; Romans 5:6,8,12-19; 6:23;
The condemnation in Adam would have been eternal had Jesus not paid the wages of sin for Adam and the human race dying in Adam. Jesus’ sacrifice -- once given over to his God -- could not be taken back. Jesus did indeed sacrifice for eternity his human body of flesh (which was prepared by God -- Hebrews 10:5) with its blood, and presented that sacrifice to his God in heaven after his ascension, thus it was important for Peter to show that Jesus is no longer flesh and blood with the terrestrial glory (1 Corinthians 15:40) that is lower than the angels (Hebrews 2:9), but that he now has the celestial glory of a spirit being, which he states is above the angels. -- Luke 22:19; John 6:51; Ephesians 5:2; Hebrews 9:24-26; 10:10; 1 Peter 3:18,22.
So what did Jesus sacrifice for our sin? Was it not his flesh? (John 6:51) Was it not his human blood and body? (Matthew 26:26-28; Mark 14:22-24; Luke 22:19,20; Acts 20:28; Romans 3:25; 5:9; 1 Corinthians 11:24,25; Ephesians 1:7; Colossians 1:14,20; Hebrews 9:12,14; 10:10; 1 Peter 1:18,19; 1 John 1:7; Revelation 1:5; 7:14) Was it not his human soul? -- Isaiah 53:12; Matthew 20:28; Mark 10:45 (Many translations render the Greek word for "soul" as "life" in some of these verses).
As a human, Jesus is dead forever; this has to be, else the Jesus never completed the sacrifice to pay the wages of sin. (Romans 6:23) It should be plain by comparison of scripture that this is what is meant when Peter said Jesus died in the flesh, but was made alive in the spirit. He is no longer flesh, having a terrestrial glory a little lower than the angels (Hebrews 2:9), since he has sacrificed his human flesh forever; he is now a spirit being highly exalted above the angels.
This is not to say that Jesus walked after the flesh while he was in the days of his flesh. (Hebrews 5:7), since he certainly was led, and he followed perfectly, God’s holy spirit (Ephesians 4:30) all the days of his flesh. (Isaiah 61:1; Matthew 4:1; Luke 4:1,14; Acts 10:38; 2 Corinthians 5:21) His walking in according with the Holy Spirit of his God was not, however, the suffering for sins that Peter spoke of. (1 Peter 3:18) Jesus maintained the human crown of glory unblemished by sin throughout the entire days of his flesh, else he could not have tasted death for all of mankind. -- Romans 5:12-19; Hebrews 2:9.
I would rather follow the Biblical position regarding the resurrection of the dead rather than the “historic” position, which is not in harmony with the basis of the atoning sacrifice of Jesus as revealed in the Bible.