When He came to earth He left everything about His God-form in heaven and came to earth as human being. So deems it fit to fullfill all that is required from Him as a human being.  He even said that He did to fulfill all righteousness.

1.  The birth of Jesus had been predicted centuries ago and His came as it was predicted. 

2.  Jesus' conception and birth was not in the normal way as others e.g through sexual relationship between man and woman, He was conceived through the Holy Spirit, and by a Math. 1 vs 18-29, Lk 1 vs 45.

3. His death and ressurection was also a proof that He is  the son of God Who came to die for the redemption of world