RE: 1 John 5:7-8. For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one. What do the three (spirit, water, and blood) represent?
John was refuting the gnostic claim that Jesus was a mere man therefore couldn’t be our Savior. The three that testify to support John’s view that Jesus was the Son of God are the Holy Spirit Who descended upon Him, the water of His baptism, a ceremonial cleansing to begin His ministry, and His shed blood by which mankind is redeemed.
At His death, water and blood issued forth from His wounded side and the Holy Spirit was given as a deposit to all who believe. Some see in this the idea that each believer is washed in the blood, baptized by water and sealed with the Holy Spirit, but the context of John’s letter is really a rebuttal against the already growing gnostic error, and these two verses clearly refer to Jesus, not us.