My dear friend, the Bible clearly teaches that our Lord Jesus did in fact exist before His human birth in Bethlehem, and His eternal existence and His deity are clearly spelled out for us in John 1:1-2 and 14; in John 8:58; in Colossians 1:14-20, and 2:9-12; in Revelation 1:17-18 and in many other verses of Scripture. Thus, if we accept God’s Word, the Bible, as true, which I do, then by faith we see that indeed, the Lord Jesus Christ was and is God, and He was always with God who is eternal, and that from the beginning as we read in John 1:1-2, “In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God.”  So, in direct response to your question as to just why the Lord Jesus had to be taught and to grow up as a child, I believe that this demonstrates His true humanity, and for all of us who trust in His finished work on Calvary’s cross for our salvation, this is critical.

He, as I said before, is true God, but when He came to the earth at Bethlehem, He veiled his glory in human flesh and became submissive to God the Father just as we humans should all be submissive to the will of God. As a true human being, He must grow and develop as any other human child, but of course He was absolutely without sin. It might be difficult for our finite minds to comprehend how the Lord Jesus could come to earth, and though while yet being fully God, He purposely took the form of a true man, which means He had to be born and grow up and learn just like any other human. Hebrews 2:17 tells us: “Therefore, in all things He had to be made like His brethren, that He might be a merciful and faithful High Priest in things pertaining to God, to make propitiation for the sins of the people.” Yet, though He had veiled His glory in human flesh, even as a child, the Lord Jesus knew very well just why He had come from God the Father as we clearly see in Luke 2:49, “And he said unto them, How is it that ye sought me? wist ye not that I must be about my Father’s business?”

He did in fact know all things as true God (see John 18:4). However, when He came to the earth as true Man, He acted as a real human man in full submission to the will and power of God the Father, not using His own place as God, but acted only in submission to His Father’s will through prayer (Matthew 26:39-42). He accomplished all His mighty works through the power of the Holy Spirit. Thus, He was true God and true Man, and as a man, He was the only perfect man ever to live in the world. It was for this reason that He could be a sin offering for us all (1 John 4:9; 2 Corinthians 5:21). Christ Jesus came into the world as a humble servant of men, and in obedience to His Father’s will. Though it appeared to the world as weakness, He went to the cross on our behalf to save sinners like you and like me (1 Timothy 1:15). William MacDonald in his commentary on Luke 2:51 said: “…The moral excellence of Jesus is seen in the words “He … was subject to them.” Though Creator of the universe, yet He took His place as an obedient Child in this humble Jewish family.  Again, we have the true humanity and normal growth of our Lord depicted: 1. His mental growth—increased in wisdom. 2. His physical growth—and stature. 3. His spiritual growth—in favor with God. 4. His social growth—in favor with men…. He was absolutely perfect in every aspect of His growth. Here Luke’s narrative skips silently over eighteen years which the Lord Jesus spent in Nazareth as the Son of a carpenter….”

The OT presents the three members of the Godhead as God, though we know from Genesis 1:1-2 and from the verses above that the Godhead was made up of three distinct persons, God the Father, God the Son, and God the Holy Spirit. Thus, when our Lord Jesus came into the world at Bethlehem as a baby in Luke chapter 2, this was not the beginning of the life of God the Son. He merely took upon Himself human flesh. He became a true Man, though He was perfect (Hebrews 4:15), being the only begotten of the Father (John 1:14). So, we know from the Scriptures that our Lord Jesus Christ was and is both true God and true man. But now why, if He was true God did He have to come down to earth as true Man? I believe the answer is so that He might be that perfect sin offering for us (2 Corinthians 5:21; 1 John 4:9). We read of the Lord Jesus that His glory was temporarily veiled in human flesh. In Philippians 2:6-8 we read: “…who, being in the form of God, did not consider it robbery to be equal with God, but made Himself of no reputation, taking the form of a bondservant, and coming in the likeness of men. And being found in appearance as a man, He humbled Himself and became obedient to the point of death, even the death of the cross.”

Only a perfect man, the sinless Son of God could be our sin offering, the Lamb of God which taketh away the sin of the world (John 1:29).  (SF)  (700.3)