1 John 5:8 And there are three that bear witness on earth: the Spirit, the water, and the blood; and these three agree as one.
The Spirit leads us to Jesus, to walk after Jesus, to live for Jesus. The water & blood could be the water baptism of Christ and the crucifixion. All testify the Person of Jesus is God. The Spirit of God was involved in these bookend events. These were the 1st and last events of Christs public ministry. What Jesus did, was on earth, to be seen by all, not in heaven, where mortal men could never see. Where is the proof of God? One only needs to look into His public life here on earth.