This is something I’ve wondered about for a while too, because it’s kind of weird how John is so adamant that water flowed from Christ’s side. He says “He who saw it has borne witness—his testimony is true, and he knows that he tells the truth—that you also may believe.” Like, why would water flowing from his side help us believe? But in the homily I heard on Good Friday this year, the priest pointed out that the water flowing from Jesus’ side is meant to be seen as a fulfillment of Ezekiel’s vision of the temple in Ezekiel 47. That blew my mind! The vision showed that from the side of the temple water flowed and “when the water flows into the sea, the water will become fresh. 9 And wherever the river goes, every living creature that swarms will live, and there will be very many fish. (Ezekiel 47:8-9)
I don’t think it’s a coincidence that throughout John’s gospel, the same Gospel that tells us about the blood and water, water is used to symbolize the life of the spirit that only Christ can give us. Or that in only John’s Gospel Jesus also explicitly identifies his body as the true temple in John 2.
So when John tells us that water was seen flowing from Christ’s SIDE, he’s not just giving us some biological detail, he’s bringing to mind the vision of Ezekiel. When the life of Christ, which we receive through water in baptism, (John 3:5) flows through us, we are “made fresh” as Ezekiel says and this grace will flow into the entire world, and every one who receives it will live. .