Paul says, "Put on the new man." What does that mean?
Sometimes familiar language in the Bible loses its meaning because it is so familiar. One example is Paul’s command to “put on the new man” (Eph 4:24). What does that even mean? And why should it be so important for how we live our lives as the context of Ephesians indicates?
To answer that question, we need to consider how paul uses “put on” language in the New Testament.
What do we put on?
If we compare Romans 13:14 with Ephesians 4:24, we can get closer to Paul’s meaning in Ephesians 4:
(1) "Put on the Lord Jesus Christ" (Rom 13:14)
(2) "Put on the new human being who was created according to God in righteousness and the holiness of truth" (Eph 4:24).
In both contexts (Rom 13 and Eph 4), Paul exhorts his audiences to live holy lives. The rationale for living holy lives arises not out of a pure moral imperative. Rather, it flows out of putting on the Lord Jesus Christ.
What does it mean to put on Christ?
In Ephesians 4, Paul's command to put on the "new man" (lit: the new human being) means to put on Christ—because Christ is the firstborn of all (re)creation. By putting him on, we are new creations (2 Cor 5:17).
Now most of us read Ephesians 4, I suspect, as a sort of moral imperative towards good behaviour (and it is that). Yet the underlying reason for our holy behaviour *is* putting on the "new human being" that Christ is. Conversely, we put off the old human being which is full of corruption (Eph 4:22).
Note: Paul claims that Christ's humanity was created "according to God" (as Gregory of Nyssa observes in his response to Eunomian’s confession of faith). This I think, incidentally, confirms that Christ did not have a fallen nature (contra Barth).
Christ's nature was fully human—yet without sin (Heb 4:15). And this is because his humanity was created "according to God"—like it was at the beginning before the Fall into sin and corruption.
Christ, the Living Spirit
So while Adam and Christ parallel each other in key respects, they do not parallel exactly. In Adam we all came to life, but in Adam’s fall, we entered into a fallen state. In Christ, we move from this fallen state into a new creation “according to God.”
Paul explains in 1 Corinthians 15:45–46:
“And so also it says, ‘The first human being, Adam, became a living psuxan’; the last Adam became a life-giving pneuma. After all, the first (human being) was not pneuma but psuxikon, then followed the pseumatikon.”
His point here, although using words now unfamiliar to us, is that Adam became a living human being (psuxan) whereas Christ became a life-giving spiritual being (psuxikon). That is, Christ’s flesh is spiritual and so can give us life by spiritual union with him.
As Jesus explains, “And the bread that I will give for the life of the world is my flesh” (John 6:51). He continues, “It is the pneuma that gives life; the flesh profits nothing” (John 6:63).
This parallels what Paul says in 1 Corinthians: “I tell you this, brothers: flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable” (1 Cor 15:50). Since flesh and blood (i.e., the fallen Adamic flesh and blood) cannot inherit the kingdom, then only a pneuma or spiritual person can. Hence, “we shall all be changed” (1 Cor 15:51).
Paul explains what this spiritual transformation looks like: “For this perishable body must put on the imperishable, and this mortal body must put on immortality” (1 Cor 15:53). It here becomes obvious that a spiritual body means an incorruptible and immortal body.
Hence, when Paul says that “flesh and blood” cannot inherit the kingdom of God, he does not deny the bodily resurrection. Rather, he denies that our resurrected bodies will exist in an Adamic state—they will be changed into a Christological state through the life-giving spirit (pneuma), Jesus the Messiah.
Christ, through his resurrection, became the firstfruit plucked for the new creation (1 Cor 15:20). We follow him. He is the firstborn of all (new) creation (Col 1:15). We are created in his image (Col 3:10; Eph 4:24) because Christ has summed up humanity in his human body. He did so for us and for our salvation.
Conclusion
In Ephesians 4, Paul then commands us to live out our future in the present. We are new creations in Christ Jesus as the Holy Spirit seals and guarantees (Eph 1:13–14). The full reality of putting on Christ means being totally recreated into the image of Christ, the pneuma, the life-giving pneuma.
So while we anticipate the fullness of new creation, we still have it in part—through the Spirit’s indwelling. So Paul can totally discount the old age in Adam now: “Neither circumcision nor uncircumcision means anything; what counts is the new creation” (Gal 6:15). Nothing else matters but Christ in us; Paul no longer identifies with the old but entirely with the new man formed in him (Gal 2:20). So should we all. And so should this transform our lives.