The flowing of the living water began from the throne. Before the rock was smitten and before Christ was crucified, the living water was already flowing from the throne. Do not think that Revelation 22:1 portrays only what comes after Exodus 17 and John 19. This is a picture of something from eternity, of something that includes the whole Bible. This indicates that the living water was flowing before the incarnation of Christ. The incarnation, however, was a further step in the flowing of the living water. God flowed from His throne into the manger and also into the home of a carpenter. Thirty-three and a half years later, God flowed through the cross and then flowed on in resurrection.
The Bible tells the story of God’s flowing. Throughout the centuries, God has been flowing, and He is still flowing today. In His flowing He passed through incarnation, human living, and death, and then He entered into resurrection. Now in resurrection He is the living water for us to drink. Therefore, the water of life we enjoy today is in resurrection. (Witness Lee, Life-Study of Exodus, ch. 42)
To drink of the water of life, we first need to be positioned to drink (1 Corinthians 12:13), and we also need to be thirsty (John 7:37; Revelation 21:6). Then we need to come to the Lord (John 7:37; Revelation 22:17), to ask of the Lord (John 4:10), to believe in the Lord (John 7:38), and to call on the name of the Lord (Isaiah 12:3-4; Acts 2:21). (Exodus 17:6, footnote 3)