Luke 1:35 - Matthew Poole's English Annotations on the Holy Bible

The Holy Ghost (who is also called here the power of the Highest) shall come upon thee; it is a phrase which signifieth a special and peculiar influence of the Holy Spirit: thus we read of the prophets, that the Spirit of the Lord came upon them, 2 Chronicles 20:14, &c., which argued a special influence of the Holy Spirit on them, efficacious, so as it put them upon a present prophesying. There is a common influence of God upon the forming of all children in the womb, Job 10:8 Psalms 139:15. But this phrase denotes an extraordinary special influence of the Spirit, changing the order and course of nature, and giving a power to the blood of the virgin by him sanctified, to coagulate alone to the forming of the body of a child: this is more mysteriously yet expressed, by the term overshadow thee, which I take to be a modest phrase, signifying only a supply of man's act, by a Divine creating power, in a most miraculous manner. Therefore also that holy thing which shall be born of thee shall be called the Son of God, as Adam was called the son of God, Luke 3:38, God (by his creating power) supplying as to him the place of father and mother, and to Christ supplying the place of the father, though not of the mother, for (saith the angel) he shall be born of thee. But yet that mass of flesh shall be a holy thing, because, though born of thee, and flesh of thy flesh, yet of thy flesh first sanctified, by the Holy Ghost coming upon and overshadowing of thee. He shalt be called so, not that he was not so by eternal generation, (of which the angel here speaks not), but the Word, the eternal Son of God, which was in the beginning, being thus made flesh, and personally united to thy flesh, the whole person shall be called the Son of God.