96 One who is pierced, a flowing fountain, the outpouring of a spirit of compassion and supplication: the first Christians inevitably considered these promises fulfilled in the pierced side of Christ, the wellspring of new life. In the Gospel of John, we contemplate that fulfilment. From Jesus’ wounded side, the water of the Spirit poured forth: “One of the soldiers pierced his side with a spear, and at once blood and water flowed out” ( Jn 19:34). The evangelist then recalls the prophecy that had spoken of a fountain opened in Jerusalem and the pierced one ( Jn 19:37; cf. Zech 12:10). The open fountain is the wounded side of Christ.
Source: Dilexit Nos (Vatican.va)