Luke 1:35

Gabriel explained that the Holy Spirit would be God’s enabling agent who would make Mary’s supernatural act of service possible (cf. Luke 1:41; Luke 1:67; Luke 1:80; Luke 2:25-27). He would overshadow Mary with His personal presence. Beyond this Gabriel was not specific.

"This delicate expression rules out crude ideas of a ’mating’ of the Holy Spirit with Mary." [Note: Morris, p. 73. For information about ideas of divine beings fertilizing human women that existed in the ancient world, see Marshall, The Gospel . . ., pp. 72-77.]

God settled upon the tabernacle in the wilderness similarly, filling it with His presence (Exodus 40:35; cf. Psalms 91:4). It is interesting that the same Greek word, episkiazo, translated "overshadow" here, occurs in all three accounts of the Transfiguration where the cloud overshadowed those present (Matthew 17:5; Mark 9:7; Luke 9:34). Then the voice came out of heaven identifying God’s Son, but here an angel identified Him as such. The Holy Spirit would produce a holy offspring through Mary. The deity and preexistence of the Son of God required a miraculous conception. His virgin birth resulted in His assuming a human nature without giving up His divine nature.