In the previous verses, God told John to write that the saved person is the one who will acknowledge that Jesus Christ is the Son of God. This is not some one who carelessly says that Jesus is the Son of God. There are many false religions that will state that Jesus is the Son of God. Their Jesus is not the Jesus of the Bible. Their phrase regarding the “Son of God” is also not based on Biblical facts. We need to remember that the devil is extremely subtil in his tactics. He is a liar. He does not know how to speak the truth. He will take words that are meant to speak truth, and he will use them in a distorted manner. John has been writing about the importance of truth. Truth is not something that is dependent on who is asking or who is listening. Truth is truth at all times. God is truth. There is no lie in God.
In verses 6-8, we have another proof that Jesus Christ is God. The perversions corrupt these very important verses. Some of them remove words and make this passage say something different. Verse 6 refers to the phrase we have noted from verse 5. Jesus, the Son of God is he that came by water and blood. Verse 6 states this as well.
To understand the reference to “water” here we need to look at other writings from John. God directed John in all his writings. “All Scripture is given by inspiration of God”. In John 3

John 3:5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.

The water in that passage refers to the process of giving birth. When a child is in the womb it is enclosed in a sack with water. The sack breaks and the water comes and then the baby is delivered. In the context of John 3, a person has to be physically alive in order to be made spiritually alive. Another possible understanding here is that the water is the Word of God. In Ephesians 5:26, the water refers to the Word of God. It is true that a person needs to hear the Word of God in order to be saved. A person is not saved by osmosis. They need to hear the truth and respond properly to the truth.
Some people assume the water is water baptism and then they use that for baptismal regeneration. No one is saved by baptism. The Bible is very clear on this.
In our text we are told that Jesus came by water. He became flesh and He went through the nine month time in Mary’s womb. His body took shape in the normal manner. He became flesh so that He could go to the cross for our sins. Jesus did not need to be saved. However, the Word of God prophesied the coming of Jesus Christ.
In our text the blood refers to the fact that Jesus Christ’s shed blood is what provides salvation for sinners. He had to become a man. He could have instantly appeared on this earth as a man, but the wisdom of God chose that Jesus Christ, the second person of the Godhead, should be born of a virgin, of a woman, and grow up as a boy into manhood and then be presented to the world as the Messiah.
In Hebrews 9:12 we read:

Hebrews 9:12 Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us.

Jesus Christ came for the specific purpose of shedding His blood for you and I. He had to be born in the flesh and He had to shed His blood in order that we could be forgiven and saved. The Holy Spirit bears witness of this fact. The Holy Spirit was there to cause conception in Mary’s womb. The Holy Spirit lighted upon Jesus Christ as a dove at His baptism. This was not to fill Jesus Christ with the Spirit, but to identify Him as the Messiah. John the Baptist referred to this in John 1:32. The Holy Spirit ministered to Jesus Christ on several occasions during His earthly ministry. The Holy Spirit is truth. The Holy Spirit is the third Person of the Godhead.
Verse 7 continues to build on these facts. There are three that bear record in heaven. All three of these are one. The Father, the Word, which is Jesus Christ, and the Holy Ghost. These three are one. God tells us this in no uncertain terms. The cults deny the deity of the Lord Jesus Christ. Some of the perversions play right into the hands of the cults. It is sad to see people who claim to know the Lord, defend corrupt bibles that seek to destroy fundamental facts that cannot be denied by those who are saved.
Verse 8 continues the argument by showing that there are three that bear witness on earth. The Spirit, the water and the blood. These three also agree in one. The Father is not on the earth. He is in heaven. The three on earth are the Holy Spirit, the water, which is referred to as the Word in Ephesians 5:26

Ephesians 5:26 That he might sanctify and cleanse it with the washing of water by the word,