5 Who is it that overcomes the world, but the one who believes that Jesus is the Son of God?
The Witness Concerning the Son
6 This is He who came by water and blood—Jesus Christ. He did not come by water only, but by water and blood. It is the Spirit who bears witness, because the Spirit is the truth. 7 There are three who testify in heaven: the Father, the Word, and the Holy Spirit, and the three are one. 8 There are three that testify on earth: the Spirit, the water, and the blood, and the three are toward the one. 9 If we receive the testimony of men, the testimony of God is greater; for this is the testimony of God which He has given concerning His Son. 10 Whoever believes in the Son of God has this witness in himself. Whoever does not believe, God has made Him out to be a liar, because he does not believe the testimony that God gave about His Son. 11 And this is the testimony: that God has given us eternal life, and this life is in His Son. 12 Whoever has the Son has life, and whoever does not have the Son of God does not have life.
Purpose of Writing
13 I have written these things to you who believe in the name of the Son of God, that you may know that you have eternal life, and that you may continue to believe in the name of the Son of God.