93 But if men have always been deeply moved by the pierced Heart of the Savior to a worship of that infinite love with which He embraces mankind -- since the words of the prophet Zacharias, "They shall look on Him Whom they have pierced,"(97) referred by St. John the Evangelist to Jesus nailed to the Cross, have been spoken to Christians in all ages -- it must yet be admitted that it was only by a very gradual advance that the honors of a special devotion were offered to that Heart as depicting the love, human and divine, which exists in the Incarnate Word.
Source: Haurietis Aquas (Vatican.va)