Is Jesus God? That's might be the most important question ever. If He is, then what He did for us on the cross and what Scripture says is true and accurate. If He's not, we're wasting our time.
What does Scripture say? The Bible teaches that Jesus is the eternal God; He was born of a virgin, lived a sinless life and died as the perfect substitute for the forgiveness of our sins. The incarnation of Jesus is the glorious central truth of redemptive history. It is the foundation of the Christian faith. Jesus Christ's life did not begin when He was born. He has existed from all eternity. The NT speaks of Jesus coming into the world, not of His coming into existence.
What Scripture teaches about salvation is that Jesus is all we need. Nothing more needs to be added, nothing more can be added. If He did not possess His divine nature on the cross, He could not and did not conquer sin and death for believers. Any teaching that denies that Jesus is God and any teaching that denies that His death was a sufficient atonement for sins, is a satanic lie.
God Himself testifies to the fact that Jesus is God. In 1 John 5:6 it says, "Jesus Christ, He is the One who came by water and blood; not by water only, but by water and by blood. And the Spirit is the One who testifies, becasue the Spirit is the truth."
The water is a reference to Christ's baptism. John the Baptist had been baptizing people in the Jordan River. He had been preaching repentance of sins and calling on the people of Israel to prepare their hearts for the coming of the Messiah. Their baptism was a public affirmation of repentance of sin. It was an external act symbolizing an internal reality.
Jesus began His earthly ministry by going to John at the Jordan River and being baptized by him. He wasn't baptized for the same reasons the people were being baptized. He had no sin to repent of and hence no need to be baptized for that reason. He was baptized to publicly identify with sinners. He was also baptized in obedience to what God had called Him to do. Jesus always obeyed the Father. He also always did whatever it was that God required of His people. This was no exception.
The blood is a reference to Christ's death. Jesus' blood was shed as a perfect sacrifice for the forgiveness of our sins. It has everything to do with who Jesus was and what He came to do.
If He wasn't God, if He wasn't the Messiah, then His shed blood doesn't mean very much at all. His sacrifice only works if Jesus truly is divine.
Then there's the Spirit. God testifies to us about the true nature of the Holy Spirit. In fact, that's one of the things said about the Spirit right here in the passage in 1 John that we looked at. It's says that the Spirit is the truth. That's a key statement. It doesn't say He likes truth or He tells truth or that truth is even just one of His attributes. He is truth, it's an essential aspect of His very being.
That's all well and good, but what does it have to do with us? What difference does it make to us that Jesus is God? All the difference in the world. If Jesus isn't God, then there is no forgiveness and there is no salvation. If Jesus isn't God, the Bible is a worthless book of fairy tales and we'd be wasting our time reading and studying it. If Jesus isn't God, there's no hope for anyone.