The Lord Jesus was completely God, but he was also completely man. This is something to be believed and not for proud reason to speculate upon. The personhood of Jesus is not a fit object for intellectual diagnosis; rather must we bow before Him in worship. He himself warned us, "No man knows the Son but the Father" (Matthew 11:27). And again, the Spirit of God through the apostle Paul declares, "Great indeed, we confess, is the mystery of godliness: He was manifested in the flesh" (1 Timothy 3:16). While then there is much about the person of Christ which we cannot fathom with our own understanding, yet there is everything about Him to admire and love: foremost are His deity and humanity and the perfect union of these two in one person. The Lord Jesus was not a divine man, nor a humanized God; He was the God-man. Forever God, and now forever man.
The deity and the humanity of the Savior were each contemplated in Messianic prediction. Prophecy represented the coming one sometimes as divine, sometimes as human. He was the Branch "of the Lord" (Isaiah 4:2). He was the Wonderful Counselor, the mighty God, the "Prince of peace" (Isaiah 9:6). The one who was to come forth out of Bethlehem and be ruler in Israel, was one whose goings forth had been from the days of eternity (Micah 5:2). It was none other than Jehovah Himself who was to come suddenly to the temple (Malachi 3:1). Yet, on the other hand, he was the woman’s "seed" (Genesis 3:15); a prophet like unto Moses (Deuteronomy 18:18); a descendant of David (2 Samuel 7:12-13). He was Jehovah’s "servant" (Isaiah 42:1). He was "the man of sorrows" (Isaiah 53:3). And it is in the New Testament we see these two different sets of prophecy harmonized.
The One born at Bethlehem was the divine Word. The Incarnation does not mean that God manifested himself as a man. The Word became flesh; he became what He was not before, though He never ceased to be all He was previously. He who was in the form of God and thought it not robbery to be equal with God "made Himself of no reputation, and took upon Him the form of a servant, and was made in the likeness of men" (Philippians 2:6-7). The babe of Bethlehem was Immanuel - God with us - He was more than a manifestation of God,; He was God manifest in the flesh. He was both Son of God and Son of Man. Not two separate personalities, but one person possessing two natures - the divine and the human.
Adapted from The Seven Sayings of the Saviour on the Cross, 5. The Word of Suffering, by A.W. Pink.