Sacramental interpretations of the blood and water from Jesus’ side are too tempting to resist. We ought not resist them. Of course, it is the blood of the new covenant and the water of baptism (John 20:34).
But the order brings us up short: Not water and blood, but blood and water. That comes from something other than sacramental imagery.
Of course is comes from the Old Testament, where Israel is redeemed by blood and then by water – first Passover, then exodus; first Passover, then Pentecost. And the same holds for Jesus: First the blood of the cross and then the rushing outpouring of the Spirit.
Jesus’ side is like Adam’s. The church is born like Eve from His side, by blood and water. When we get Israel into the typological mix, we can confirm that Israel birth in blood and water is a birth as Bride.
Passover plus Exodus equals the new Eve that is Israel.