1. Water - Jesus' baptism in the Jordan River, when the Father spoke from Heaven - Matthew 3:13-17
2. Blood - the historical death of Jesus on the cross - John 12:28-33
3. The Spirit - given to bear witness of Christ - John 15:26; 16:14
1 John 5:6-13; NKJV
6 This is He who came by water and blood — Jesus Christ; not only by water, but by water and blood. And it is the Spirit who bears witness, because the Spirit is truth.
7 For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these three are one.
8 And there are three that bear witness on earth: the Spirit, the water, and the blood; and these three agree as one.
9 If we receive the witness of men, the witness of God is greater; for this is the witness of God which He has testified of His Son.
10 He who believes in the Son of God has the witness in himself; he who does not believe God has made Him a liar, because he has not believed the testimony that God has given of His Son.
11 And this is the testimony: that God has given us eternal life, and this life is in His Son.
12 He who has the Son has life; he who does not have the Son of God does not have life.
13 These things I have written 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.