In a previous post I wrote the following about the Mormon doctrine on the incarnation:
They also deny the virgin birth: “The birth of the Saviour was as natural as are the births of our children; it was the result of natural action. He partook of flesh and blood—was begotten of his Father, as we were of our father” (Journal of Discourses, vol. 8, p. 115). They believe that the Heavenly Father, of flesh and blood, impregnated Mary in the manner of regular conception.
Since then I have learned a couple of things. First, the LDS church does not hold that the teachings in the Journal of Discourses are doctrine. Second, the LDS church does believe that Mary was a virgin when she gave birth to Jesus. The Book of Mormon teaches:
And he said unto me: Behold, the virgin whom thou seest is the mother of the Son of God, after the manner of the flesh. (1 Nephi 11:18; see also Alma 7:10)
The position of the Mormon Church is Jesus the Son of God is the literally the son of God the Father, who they believe has a physical body. Thus mysteriously, 23 chromosomes of Heavenly Father’s DNA joined with 23 of Mary’s to make the Person of Jesus Christ. (I found this to be a helpful post.)
The Bible does, in fact, teach that the incarnation was a mysterious act of God by the power of the Holy Spirit in the body of Mary. Historical Christianity rejects the idea that God the Father has a corporeal body and believe in the unity of the Father, Son, and Spirit in the doctrine of the Trinity. Thus the incarnation was the act of God becoming man. The Father sent the Son to be born of a virgin by the power of the Spirit.
Does this distinction matter? I believe it does. The biblical doctrine of the incarnation maintains that God alone can save:
And there is no other god besides me,
a righteous God and a Savior;
there is none besides me.
By believing that Jesus the Son and the Heavenly Father are two Persons of the one divine Being, we see that in the coming of Jesus, God Himself came to earth to save. The LORD alone is Savior, who by the power of his Spirit and the work of the Son makes us his children and reconciles us to himself.
I apologize for misrepresenting the Mormon position on this matter, and I will do my best to correct it when I hear of it in the future.