I had heard that each of the gospel writers wrote their gospel in order to testify of Jesus, yes, and tell what they had been eyewitnesses of, but also to bring out a certain aspect of the Lord’s identity. Matthew showed that Jesus was the Son of David, the promised Messiah. Mark showed that Jesus was the Son of God; and we can see that this is in fact one of the first things Mark says about Jesus in vs. 1. By the way, Luke showed that Jesus was the Son of Adam, the Son of Man, the Savior for all mankind, and not just Jews only. And John showed that Jesus was in fact YHVH come in the flesh; that He was fully man, and fully God, in one person.
Other details that Mark brings out to show that Jesus is the Son of God:
He will come baptizing with the Holy Spirit (vs. 8), something no mere king of Israel, even of David’s line, ever did or claimed to do.
Immediately when Jesus was baptized, the voice from heaven declared, “You are My beloved Son, in whom I am well pleased.” (vs. 11).
Jesus came and preached the kingdom of God, not the kingdom of David (vs. 15).
He taught as one with authority (vs. 22), which their scribes did not do. Yes, because He is the Living Word!
He also, with authority, cast out demons, and they obeyed Him (vs. 27).
Even the demons testified that He was the Holy One of God (vs. 24).
Fevers and all manner of diseases were healed by His authority (vs. 29-34).
He also healed uncleanness (vs. 40-41). The leprosy spoken of here is not the same as the disease of leprosy that we normally think of, but an uncleanness brought about by sin which kept people separated from the congregation of Israel (Lev 13). God separates light from darkness (Gen 1:3-4), the holy from the common (Exo 20:8-11), and the clean from the unclean (Lev 10:8-10). He even had to separate Himself from Adam after Adam sinned, because sin does not dwell with God (Gen 3:22-24, Isa 59:2). But the Son of God came to HEAL the uncleanness and END the separation!
The Son of God upheld the Law of God. He rested on Sabbath and told the lepers to show themselves to the priests as the Law commanded (vs. 32, 44).
Now why is the witness of the four Gospel writers, as to the identity of Jesus, so important? What does it matter if someone thinks He was only a man, or only God, or only of David? I think it is important, because only One who was God, and man, the Son of God, of Adam, and of David, could accomplish all that the prophets have prophesied about Messiah. Whatever aspect of His identity is denied, there is a corresponding heresy that either restricts salvation, restricts His glory and worship, or restricts His authority and power over His enemy Satan. The heresies diminish Him or diminish what He has accomplished for us on our behalf! The gospels which have been inspired by the Holy Spirit, reveal His nature and character, as it is necessary for us to learn and know Him!