luke 1:35 And the angel answered and said unto her, 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. - Free Bible Online

      35. Holy Ghost--(See on Mt 1:18).
      power of the highest--the immediate energy of the Godhead conveyed by the Holy Ghost.
      overshadow--a word suggesting how gentle, while yet efficacious, would be this Power [BENGEL]; and its mysterious secrecy, withdrawn, as if by a cloud, from human scrutiny [CALVIN].
      that holy thing born of thee--that holy Offspring of thine.
      therefore . . . Son of God--That Christ is the Son of God in His divine and eternal nature is clear from all the New Testament; yet here we see that Sonship efflorescing into human and palpable manifestation by His being born, through "the power of the Highest," an Infant of days. We must neither think of a double Sonship, as some do, harshly and without all ground, nor deny what is here plainly expressed, the connection between His human birth and His proper personal Sonship.

JFB.