96 It is enough to recall the record of that age in which the devotion to the Sacred Heart of Jesus began to develop to understand clearly that its marvelous progress has stemmed from the fact that it entirely agreed with the nature of Christian piety since it was a devotion of love. It must not be said that this devotion has taken its origin from some private revelation of God and has suddenly appeared in the Church; rather, it has blossomed forth of its own accord as a result of that lively faith and burning devotion of men who were endowed with heavenly gifts, and who were drawn towards the adorable Redeemer and His glorious wounds which they saw as irresistible proofs of that unbounded love.
Source: Haurietis Aquas (Vatican.va)