The angel answered her, "The Holy Spirit will come on you, and the power of the Most High will overshadow you. Therefore also the holy one who is born from you will be called the Son of God.
This whole paragraph regarding the annunciation is fantastically beyond the power of any mere human being to have invented it.  Like many other passages in the Bible, this lies utterly beyond the perimeter of anything that the natural man might have imagined.