Excerpt from an article by Dr. Henry M. Morris:
When God Became Man
How Could the Creator Become Man?
Since "by Him [that is by Christ, the Word of God] were all things created, that are in heaven, and that are in earth"
(Colossians 1:16), He must have created the very body in which He would dwell when He "was made flesh." This body, however, could not be a body produced by the normal process of human reproduction, for it must be a body unmarred either by inherent sin spiritually or by inherited genetic defects physically or mentally.
It would necessarily have to be a perfect body, a body like that of the first man He had created long ago in the beautiful garden of Eden. He would, in fact, come to be called "the last Adam"
(I Corinthians 15:45), since there would never be another man created as that "first Adam" had been.
There would be one important difference, however. The first Adam was created and made as a full-grown man, but the second must be "in all things . . . made like unto His brethren"
(Hebrews 2:17). From conception to death, He must be "in all points . . . like as we are, yet without sin"
(Hebrews 4:15). In particular, His blood must be "precious blood . . . as of a lamb without blemish and without spot"
(I Peter 1:19), for that blood must be "offered . . . without spot to God"
(Hebrews 9:14).
Thus the body of the second Adam must be formed directly by God and placed in a virgin's womb. This had been the very first promise made after the first Adam brought sin and death into the world. Speaking of "the woman, and . . . her seed," God said that He "shall bruise thy head, and thou shalt bruise His heel"
(Genesis 3:15). This prophecy was addressed to Satan, whose lie had elicited Eve's sin.
This wonderful body would not grow from a man's seed, as in every other human birth, nor would it grow from a woman's egg, for in either case a sin-carrying and mutation-carrying embryo would necessarily result. It must instead be a seed specially formed by the Creator Himself, then planted in the virgin's womb, where it forthwith would become His "tabernacle" for thirty-three years as He lived on His planet Earth among those He had come to save.
"Lo, I come," He would later promise through David
(Psalm 40:7). Through Isaiah He said: "(The) virgin shall conceive, and bear a Son," and that babe would also be "the mighty God, the everlasting Father"
(Isaiah 7:14; 9:6). Still later, another great prophet could anticipate that "The LORD hath created a new thing in the earth, a woman shall compass a man"
(Jeremiah 31:22).
Note that the "new thing" in the chosen woman must be
"created." When the time came the angel assured young Mary that "The Holy Ghost shall come upon thee, and the power of the highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be called the Son of God"
(Luke 1:35).
Then, "when He cometh into the world, He saith, . . . a body hast thou prepared me"
(Hebrews 10:5). Most significantly, He used the same word "prepared" (Greek,
katartizo), which the writer of Hebrews also then would use when he testified that "the worlds
were framed by the Word of God"
(Hebrews 11:3), recognizing that the same living Word who had framed the worlds had also framed His own human body! And in that tiny cell in Mary's womb resided all the information not only for His own growth into manhood, but also for the creation, preservation, and redemption of the whole creation. It was His by right of creation and soon would be doubly His by right of redemption.
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Bolding is mine