Rivers of Living Water

The Gospel of John was the first book in the Bible that I read in its entirety after I became a Christian. In this Gospel, Jesus said the following:

In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink. He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water. (But this spake he of the Spirit, which they that believe on him should receive: for the Holy Ghost was not yet ...