Shorter Catechism Q. 22. How did Christ, being the Son of God, become man? A. Christ, the Son of God, became man, by taking to himself a true body and a reasonable soul, being conceived by the power of the Holy Ghost in the womb of the virgin Mary, and born of her, yet without sin.
Commentary: God becoming a human being was an extraordinary, wonderful, inscrutable event. What we do know about it is that the Son, the second person of the Godhead, became a complete, whole, or true human being.
Firstly, this means, as the Catechism says, that the Son of God took to himself “a true body.” During the early days of the Church, some (called “Docetists”) argued that the Son only appeared or seemed to have body because they believed that the divine could not be joined to a physical, material body. The Scriptures, however, clearly teach that Jesus has a human body like us because like us he drank, ate, slept, bled, and died. Moreover, to deny that the Word became flesh (John 1:14), and to deny that Jesus Christ has come in the flesh (1 John 4:2) is to reject the truth of God and is to imbibe the teaching of false prophets and the spirit of the antichrist (1 John 4:1-3).
Secondly, this means that the Son of God took to himself “a reasonable soul.” Other people agreed that Jesus has a human body but argued that he didn’t have a human soul because the divine nature took its place. But again, the Scriptures clearly teach that Jesus has a human soul like us because like us he grew in knowledge and wisdom, he marveled, and his soul was very sorrowful.
Although Jesus is like us in that he is a true human being, he did have a unique conception. He was “conceived by the power of the Holy Ghost in the womb of the virgin Mary.” He then had a normal development in the womb and birth: “and born of her.”
Still another way in which Jesus is not like us is that he was born without sin. We were “brought forth in iniquity, and in sin did [our] mother[s] conceive [us] (Ps. 51:5).” But not so with Jesus. He was and is “innocent, unstained, separated from sinners…without sin, (Heb. 7:26, 4:15).”