It had to be a human—it was essential to the plan. God had promised a human that they would have a human descendant that would fix the human problem of sin and do away with the human consequence of death. It was all a human paradigm that required a human answer. But as the centuries progressed, humanity proved that there was nothing they could do to fix things, for every single human sinned and was therefore subjected to death. But this was one prophecy that God would not let fade away.
All of the spiritual beings of Heaven fit within the Old Testament classification of, “the sons of God” or “holy ones.” They were all God’s heavenly family, and therefore, God’s holy children. For that reason, Mary’s head may have been spinning when an angel (a holy son of God) appeared to her and told her that (despite her virginity) she would miraculously have a baby, “called holy—the Son of God.” Yes, these specific words would have made Mary realize that the long-awaited descendant of King David was about to be created inside of her since these titles evoked such prophecies—but there was something even crazier happening: A spiritual being—a holy Son of God—was allowing himself to become fully human inside of Mary’s womb. After all, it had to be a human that solved the human problem. And since humanity had proved incapable of fixing sin, a Son of God would go to earth, become human, and do it himself.
In fully-human form, this spiritual being went by the name of “Jesus.” And since he managed to solve the human problem we consider him thee Human of humans. But in fully-spiritual form, this spiritual being went by the title, “The Angel of the Lord.” Within the Heavens, he was thee Son of God of the sons of God—thee Angel of angels. But he was more than a mere angel, which was absolutely necessary since angels were known to sin and wouldn’t be able to fix the human problem simply by the fact that they were angels. Thee Angel of angels was needed because, as many theologians point out, whenever this specific angel appeared or spoke throughout the Old Testament, the lines were always blurred as to if this angel was speaking on behalf of God, or was God Himself. Upon close inspection of all the passages about this Angel, it becomes very clear that the Angel of the Lord is God.
And so, thee Son of God, known as the Angel of the Lord, who was fully-God in spiritual form, subjected himself to the womb of Mary, and took on human flesh—still being fully God in identity, but now in human form. This is the incredible miracle we celebrate at Christmas.