4 For those who were listening to Jesus speaking, it certainly was not difficult to relate these words by which He promised the fountain of "living water" destined to spring from His own side, to the words of sacred prophecy of Isaias, Ezechiel and Zacharias, foretelling the Messianic Kingdom, and likewise to the symbolic rock from which, when struck by Moses, water flowed forth in a miraculous manner.(4)
Source: Haurietis Aquas (Vatican.va)