Lately, a dear friend wrote a quote saying, “If it is true that the male is made up of boys and men, however it is a boy by birth but man by decision!”
There are two types of men: there is the natural man and the spiritual man. I will incorporate another word to help explain my point. When I use the word “complete” man I mean the person who adds the spiritual dimension to his natural life. First a man is a boy by birth; he then becomes a man with time. However, the mature man must also become a complete man. The complete man is the one who adds the spiritual dimension to his life.
Nicodemus was a mature and religious man; but he was not a spiritual man. One day by night he came to Jesus. Remember that Jesus was one the only man to be a complete man from the beginning. Why did he come from heaven to us? He came to tell us how to become complete men. We read in John 3:6 Jesus explaining to Nicodemus that “Flesh and blood gives birth to flesh and blood, but the Spirit gives birth to things that are spiritual.” The complete man is a person in whom the Spirit of God gives birth to his spiritual dimension. The spiritual dimension was lost when Adam and Eve ate the forbidden fruit in the Garden of Eden. Jesus, the man from heaven, came to show to the natural man how to become a spiritual man.
The complete man, not surprisingly, wants to become a disciple of Jesus. A disciple’s desire is to dedicate his life to the Savior. Romans 12:1 explain how to avoid conformity and to choose transformation instead. There must be that once-and-for-all dedication of the person and his body to the Lord. That means letting him deny himself and taking up his cross daily.
Arnold G. Fruchtenbaum wrote, “The dedication of a man’s body has two elements; a negative one and a positive one. Negatively, the commitment is: denying himself. That means, “Saying ‘no’ to himself,” and that is what happens when a man dedicates himself and his body to the Lord. Then the positive of the commitment is: taking up his cross daily. To “take up the cross” means to identify with the Messiah, more specifically with His rejection.”
The complete man concept does apply to woman as well.
 Arnod G. Fruchtenbaum, The Messianic Bible Study Collection, vol. 140 (Tustin, CA: Ariel Ministries, 1983), 9