John 7:37-39

³⁷On each of the seven days of the celebration, the high priest poured out some water on the altar in the Temple to remember how God provided water for the people in the desolate area long ago. But the water he poured did not help anyone who was thirsty. So on the last day of the festival, which was the most important day, Jesus stood up in the Temple courtyard and said with a loud voice, “Those who are thirsty should come to me to drink what I will give them.

³⁸Just like the Scriptures teach, streams of water shall flow out from within those who believe in me, and that water will cause them to live eternally.”

³⁹When Jesus said that, he was referring to God's Spirit, whom those who believed in Jesus would receive later. Up to that time God had not sent the Spirit to live within believers, because Jesus had not yet died and returned to his glorious home in heaven, from where he would send the Spirit.