37 On the last day of the feast, the great day, Jesus stood up and cried out, “If anyone thirsts, let him come to me and drink. 38 Whoever believes in me, as  the Scripture has said, ‘Out of his heart will flow rivers of living water.’” 39 Now this he said about the Spirit, whom those who believed in him were to receive, for as yet the Spirit had not been given, because Jesus was not yet glorified.(John 7:37-39 (ESV)
“Out of his heart will flow rivers of living water.” The feast of Booths was a seven day event in which a priest would start out each day filling a gallon jug from the pool of Siloam and process in a parade up to the temple to pour the water out on the altar. On the Seven day they would circle the altar seven times before pouring the water singing: “With joy you will draw water from the wells of salvation. (Isaiah 12:3 (ESV). It was on this occasion that Jesus stands up and makes his statement: “If anyone thirsts, let him come to me and drink, and whoever believes in me, as the scripture has said, ‘Out of his heart will flow rivers of living water.”
John explains, Jesus is talking about the Spirit those who believe in him were to receive. The Spirit had not yet been given. It’s amazing how often water and the Spirit are linked in scripture, even at the very beginning the Spirit is hovering over the water. But the link is clear, when baptism is considered. These are the living waters that flow from the hearts of believers who are all baptized. This is the flood of grace that saves, the wells of salvation. And it is in this manner the spirit could not be given until Jesus Christ was glorified. Jesus had to undergo his own baptism before baptism with the spirit could be given. He had to die and rise again, that in our baptism we could be buried with him into his death, so that just as he rose from the dead to the glory of the Father, we too might walk in the newness of life. (Romans 6:4) It is in his death and resurrection that Jesus is glorified. And this marks the separation from John’s baptism and that of Jesus. Christians aren’t baptized with John’s baptism of repentance, but we are baptized by the one who baptizes with the Holy Spirit and fire, in living waters of salvation. And now those waters flow from our hearts. They flow from our hearts as the Spirit proceeds from our lips sharing the gospel with neighbors, friends, coworkers and family. And those who thirst come to Jesus to drink the living waters that well up to eternal life, never again to be thirsty but knowing that in baptism they have received eternal life, and walk in the newness of life that comes with forgiveness.