The Lord frequently says that the Father “sent” him, or that he “was sent” by the Father (for example, Matthew 10:40; 15:24; John 3:17, 34; 5:23, 24, 36, 37, 38; 6:29, 39, 40, 44, 57; 7:16, 18, 28, 29; 8:16, 18, 29, 42; 9:4; and very often elsewhere). The Lord says this because “being sent into the world” means coming down among people, which he did through the human manifestation he took on through the Virgin Mary.
The human manifestation really is the Son of God, in that he was conceived by Jehovah God as the Father, as it says in Luke 1:32, 35.
He is called “the Son of God,” “the Son of Humankind,” and “the Son of Mary.” “The Son of God” means Jehovah God in his human manifestation. “The Son of Humankind” means the Lord in his role as the Word. “The Son of Mary” properly means the human manifestation he took on. Just below we will show that “the Son of God” and “the Son of Humankind” have the meanings just mentioned. As for “the Son of Mary” meaning just the human manifestation, this is obvious from human reproduction. The soul comes from the father, the body from the mother. The soul is in the father’s semen; it is clothed with a body in the mother. To put it another way, everything we have that is spiritual comes from our father; everything physical comes from our mother.
In the Lord’s case, the divine nature he had came from Jehovah his Father; the human nature he had came from his mother. These two natures united together are “the Son of God.” The truth of this is clearly substantiated by the Lord’s birth, as recorded in Luke: “The angel Gabriel said to Mary, ‘The Holy Spirit will descend upon you and the power of the Highest will cover you; therefore the Holy One that is born from you will be called the Son of God’” (Luke 1:35).
Another reason why the Lord described himself as “sent” by the Father is that “someone who has been sent” has a similar meaning to “an angel.” The word “angel” in the original language means “one who has been sent.” [The Lord] is said to be [an angel] in Isaiah, “The Angel of the Faces of Jehovah has freed them. Because of his love and his mercy he redeemed them” (Isaiah 63:9); and in Malachi, “Suddenly the Lord will come to his temple—the One you seek, the Angel of the Covenant, whom you desire” (Malachi 3:1); besides other passages.
Where we discuss the divine Trinity below in chapter 3 of this work [Sections 163–188] it will become clear that the divine Trinity—God the Father, the Son, and the Holy Spirit—exists within the Lord; the Father in him is the divinity he draws on, the Son is his divine human manifestation, and the Holy Spirit is the divine power that radiates [from him].
from True Christianity, Section 92