Witness of the Holy Spirit
Vs. 5:6 – This is the One who came by water and blood, Jesus Christ; not with the water only, but with the water and with the blood.It is the Spirit who testifies, because the Spirit is the truth. -
Water and blood: refers to his physical birth and physical death. See Gen. 9:4, Lev. 17:11, 1. That Jesus came and became a living breathing human being is important. One of the heresies (e.g., Gnosticism and others) about the savior is that He was not really a human, but was a spirit appearing to be a human. The problem with this line of thought is the debt of sin cannot be paid without a death. That was the purpose of the sacrifices - the atonement. It is not possible for a spirit being to atone for human sins. A spirit being would have no blood. Fake blood (the appearance of blood, but not really) has all the efficacy of a movie stunt gimmick. Exploding packet of red dye appear real, but are not. How many times have you seen this in Mission Impossible movies and TV?
Where does the 'water' fit into this testimony? There are a couple of possible explanations. It has been noted that this passage has been controversial since it was written. Much better theological scholars than I have debated the meaning. Oh well, here goes... I believe there are two or three most likely explanations.
The first is the water refers to natural birth - there is a 'water' that surrounds the baby in the womb. (I do not know if the placenta water is simply water, or has other nutrients for the baby's growth, but we all know about 'the water breaking' indicating impending birth.) This shows that Jesus was a real baby human, born of a human mother.
Another reference to water is the baptism of Jesus in the gospels (Matt. 3:13-17, et. al.). Jesus did not need to be baptized for repentance like the others who were listening and believing John the Baptist. He did this to show us that we could identify with Him, or He identified with us.
Another possibility regarding the water has to do with the events of the crucifixion. Specifically when the Roman soldier pierced Jesus' side and 'water and blood' flowed down.
It was not enough for Jesus just to be on earth. So have several billion humans, but all the rest were not sent from God for us. All the rest did not die for our sins. All the rest did not resurrect from the dead to life, or receive approval from God to be exalted to the throne. (1 Tim. 3:16)
(Side note: it is said by many, many teachers that we know that Jesus now knows how we feel because He too was human and felt and suffered as we do. He knows what it is to be human. To say that Jesus had to be human in order to identify with us, limits the omniscience of God, Jesus, and the Holy Spirit. This line of thinking is a version of "don't judge a man until you have walked in his shoes"; or God cannot really know pain, or loss, or suffering unless He became human. Really? Really? I think that it is more for us to trust Him, than for Him to finally comprehend what it is to be human. We can now look to Jesus and think,"Ahh, He now knows what I am going through. I can trust Him to want to help me." Again, I believe this is for us, since we have difficulty believing that others can completely empathize unless they have gone through what we have gone through. It is for us because we are so untrusting we cannot believe that God could love us unless He has experienced the trials and tribulations we face. Our ignorance or limited understanding of omniscience - complete and perfect knowledge of everything that ever was, is, or will be, requires that we come up with these types of explanations.) 
Vs. 5:7, 8 – For there are three that testify:
the Spirit and the water and the blood; and the three are in agreement. -
verses 7 and 8 go together, making little sense alone. (Verse 8 kind of stands alone, but the two are one sentence.) It appears that verses 6-8 are a set. Verse six speaks of the advent of the Messiah, Jesus Christ. Water, blood, and Spirit - how are these tied together in testimony, and how do they apply? Above, in verse six, I said the water and the blood were references to Jesus's birth and death. See Matt. 1:20. They also could apply to his baptism - the beginning of His ministry - and his death, sacrifice on the cross - the completion of His ministry. See also John 3:5.
The Holy Spirit is the One that draws our Hearts and minds to salvation. We do not come to salvation on our own - we can't, we're sinners. In the OT, very few believers received the Holy Spirit - the prophets, some of the Judges, the artisans that fabricated the Tabernacle. It does not appear that the Holy Spirit was manifested in all of the Jews, or other believers. This filling and empowering by the Holy Spirit for all believers is new, a 'mystery' (a mystery is a new revelation from God to believers that was not mentioned or understood from prophecy or revealed in the OT. The 'church' is a good example. That the Messiah would die for our sins, or that Gentiles would be welcomed are not mysteries - these were revealed but improperly understood). That the new covenant would result in the church, the body of believers, distinct from the Jews of the old covenant is a new revelation - therefore, a 'mystery'. Jesus reveals that the Holy Spirit will be with us, fill us, teach us and guide us - this too is a 'mystery' since this phenomenon is new and not clearly prophesied in the Old Testament.
In Acts we see the church grow both spiritually and physically by the power of the Holy Spirit - Acts 1:5, 8; 2:4, 38.
It started in Jerusalem, spread to Samaria, and the rest of the world (Gentiles) - Acts 8:7, 29; 19:2. Paul writes in Romans 8:2, 16, and 17 that the Holy Spirit is the one that moves and convicts. It is the Holy Spirit who leads us in all things related to Jesus and the Father because the Spirit has access to everything in God's name - EVERYTHING (1 Cor. 2:10, 12). But we are a stubborn and stiff-necked people. Even as Jesus was doing miracles, healing and casting out demons, there were many who would not believe He was the Messiah (John 10:25-38).
If you cannot believe His testimony, His words about Himself are true - that He is God, and He has come to save us from our sins - why doesn't the physical evidence, doing miracles that only God can do cause you to believe? If words don't work, then miracles should convince.
Vs. 5:9 – If we receive the testimony of men, the testimony of God is greater; for the testimony of God is this, that He has testified concerning His Son.
"we receive the testimony" - This is a reference to legal issues. The testimony of one witness was not sufficient to make a judgement in Jewish law. Even in American jurisprudence, two witnesses is much better than one. We have the testimony of the apostles (see: 1 John 1:1-4, John 1:1-11, Rom. 11:13; 1 Cor. 9:1). The apostles were protective of the gospel - always aware if a teacher was not preaching the 'true gospel', or 'my gospel'. (Rom. 16:25; 2 Tim. 2:8). The most powerful testimony of our faith in Jesus is the change He has made in our lives. This is said very clearly in Hebrews 2:3-4 - how will we escape if we neglect such a great salvation? It was first communicated through the Lord and was confirmed to us by those who heard him, while God confirmed their witness with signs and wonders and various miracles and gifts of the Holy Spirit distributed according to his will.
Vs. 5:10 – The one who believes in the Son of God has the testimony in himself; the one who does not believe God has made Him a liar, because he has not believed in the testimony that God has given concerning His Son. -God inserts the Holy Spirit within us, confirming with our spirit, when we believe and accept Jesus as Lord. We need no other proof than the Holy Spirit. He has been given to teach and help and guide us through our Christian life. See John 14:13-17.
"the one who does not believe God has made Him a liar," - This is an interesting construct. Choosing NOT to believe that Jesus is the Messiah has deeper ramifications than just saying, "I don't want to believe." Why do we say that we do not believe someone, especially someone who giving testimony, corroborating evidence to an issue? There are several reasons: the answer may be beyond our understanding (a detailed explanation of pi mesons, or bosons, or Schroedinger's cat). The information is too fanciful (time travel, Tarot cards or astrology). We do not know the person giving the testimony, or know his curriculum vitae (does this person have the background to be accepted as knowledgable in this matter?). We may know this person to be less than truthful (Bill Clinton, Sen. Harry Reid, ex-Gov. John Kitzhaber). There may be more reasons, but you get the point. Do any of the above reasons apply to the Lord? No.
Well, maybe trying to understand why He would want to save us, sinners all. That may be beyond our understanding, despite all the explanations given in scripture. God has told us what He has done. God is not a man, so he cannot lie. Num. 23:19 He has not lied to us, so there is no reason to doubt His promise. There are ample examples of His faithfulness in the Bible. But we do not need to just believe what we are told, or read, because there is the following:
What is the proof? The proof of our faith is that we now have eternal life. We got it from and through Jesus. In some ways, that is the icing on the cake. We have received as a result of our belief, release from shame and the guilt of sin. We have received the Holy Spirit as a earnest agreement, a guarantee the eternal life is ours. With the Holy Spirit we also receive the power, ability to live in a manner worthy of the sacrifice made. We have received peace - the peace with God and the peace of God. We no longer need to fear what will happen when judgment comes. We can also face the trials we encounter as we go through life. Eternal life, being in the presence with the Father, the Son and the Holy Spirit is the big prize, and I do not want to trivialize that. Paul emphasizes this in 1 Cor. 15:19 For if only in this life we have hope in Christ, we should be pitied more than anyone.
The peace of God in our present life is wonderful, beyond compare. But if that is all there was to it, if that is all we have to hope for (which is an existentialist point of view) we are really big losers! If that is all you see, you are missing the big picture, the whole point of Scripture, the reason for Christ's life, death and resurrection. God wants us to be with Him! The God who speaks universes into being, who is glorious beyond imagining wants to be with us. He wants us to be with Him! He took the effort to prove it. Eternal life is not just 'Pie in the Sky, bye and bye', we can know it now and live accordingly. Stephen Covey in Seven Habits of Highly Effective People wrote that you stop to consider what you want people to think of you when you die and live accordingly (that's a paraphrase). We know what is in store for us, and can live accordingly - not in profligacy but in a manner worthy the price and the glory.
Jesus himself said that He was was the way, and the truth, and the life; that there was no other way to eternal life. (John 14:6). This is really straightforward, simple. Either you have Christ, or you don't. It's black or white. Yes or no. There is no maybe yes, maybe no. It is not a bell curve. It is not a matter of balance scale - the good out weighs the bad, or vice versa. There is no comparison of my life to another's. Is my name written in the Lamb's Book of Life? See Rev. 20:11-15; 21:27; 13:8. From the old jazz song "Is you is, or is you ain't..."
We Can Know!Vs. 5:13 – These things I have written to you who believe in the name of the Son of God, so that you may know that you have eternal life. -
This is a summary of what was said beforehand. - This letter is one long encouragement. It is written to believers to help them see and know they are blessed and to live so. See also Mark 2:10, Luke 8:10, John 10:38, and John 20:31. The truth is out there! (Sorry about the 'X-Files' reference...)