The Spirit is the flow of the Trinity, the realization of the Son for His reaching and entering into His believers (John 7:38-39; Rev. 22:1; John 14:16-20). The Father is the source, the Son is the course, and the Spirit is the flow. The source, the course, and the flow are according to the notion of our Triune God as the living water, which eventually becomes a river. At the end of the Bible, in the very last chapter, our Triune God is shown as a flowing river, the river of water of life (Rev. 22:1). Such a flowing river has a source, a course, and a flow. The source, the course, and the flow are three aspects of the one river.
In 1977 I visited Israel with a group of brothers. One day we went to the source of the Jordan River at the foot of Mount Hermon. There is a spring there with a fountain as the source. The spring has a flow, and the flow is a stream, a river. Such a river is a picture of our Triune God with the Father as the source, the Son as the course, and the Spirit as the flow. This is the biblical illustration in Revelation 22.
In Revelation 22:1 the Son is the Lamb, indicating that the Son is the Redeemer. The river of water of life proceeds out of the throne of God and of the Lamb. There is one throne for both God and the Lamb, signifying that God and the Lamb are one—the Lamb-God, the redeeming God, God the Redeemer. Revelation says that the Lamb is the lamp (21:23), and God is within Him as the light (22:5). Thus, God is in the Lamb on the throne, and out of His throne flows the river of water of life, the Spirit. When the Spirit flows it carries the Lamb. Then in the flow of the river, the Lamb becomes the tree of life (Rev. 22:2). The tree of life growing on the two sides of the river signifies that the tree of life is a vine, spreading and proceeding along the flow of the water of life for God's people to receive and enjoy. The tree of life symbolizes the Triune God to be our life supply. The Triune God is the water of life for us to drink and the tree of life for us to eat.
At this point I want us to realize that we should not study the person of God in an objective, theological way. We should not study the Divine Trinity as a mere doctrine. The Bible shows us that the Divine Trinity is for our enjoyment. Second Corinthians 13:14 says, "The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all." This verse mentions three things: grace, love, and fellowship. Actually, however, this is one thing in three aspects. The source is the divine love, the course is the divine grace, and the flow is the divine fellowship. Out of God the Father flows the grace through Christ. Then this grace flows in the fellowship of the Spirit. Second Corinthians 13:14 shows us three persons in three aspects: God the Father, Christ, and the Spirit; and love, grace, and fellowship. God the Father as love is the source, Christ as grace is the course, and the Spirit as fellowship is the flow. At the end of the Bible, we see our Triune God flowing forever. His flowing is for the purpose of supplying His redeemed with Himself as drink and food so that we may enjoy Him as the bountiful supply. In the beginning of my Christian life I did not realize this. But today I fully realize that we need to experience, enjoy, and express the Triune God—the Father, the Son, and the Spirit.