To be hidden in union with Christ demands death to sin because we have put off the old man and put on the new. John Calvin defines the "old man" as whatever we bring from our mother's womb, and whatever we are by nature." In this context, it designates the unregenerate state in which there is no spiritual life or sensitivity and no impulse toward God or spiritual things. It is that nature that gives rise and expression to every evil deed.
The simple fact of the matter is that those who trust Christ don't wear those clothes anymore. No longer are they spiritually dead, insensitive, or motionless toward God. They look different because they have put on the new man.
The "new man" refers to that regenerate nature in which the Holy Spirit has implanted the principle of spiritual life. It is the new garment worn by everyone hidden in Christ. Paul describes in the new man as being continually, habitually, progressively renewed in the knowledge of the Creator's image. It is not a sinless nature, but wants to be and is headed in that direction.
It is beyond the scope of our meditation here to think about the full meaning and many implications of the image of God. Suffice to say that it was the unique mark of man's original creation that was tragically marred by the fall of man into sin and wonderfully restored by God's grace through the gospel. Jesus Christ is the ideal image, even the perfect manifestation of God (Colossians 1:15), and it is only through Him and in Him that we are being renewed. Christ, the Second Adam, reversed the curse and restored all lost by the first Adam.
So, regardless of race or nationality (Colossians 3:11), every believer looks the same in this regard: they have all put on the new man. To wear the new man is to be adorned with Christ, who is all and in all: He is our uniform. Christ is everything in the realm of grace; there certainly is no experience or enjoyment of grace without Him. We die to sin by looking to Christ. As we look, we are changed progressively from glory to glory (2 Cor. 3:18)until He appears, when we will be like Him because we see Him as He is (1 John 3:2). If seeing Christ with our eyes is how glorification works, it follows that seeing Christ with the eyes of faith is how sanctification works. There is something about seeing Jesus that makes us like Him." pg 11,12 Michael Barrett "The Beauty & Glory Of Christian Living" Edited By Joel R. Beeke