The Solemnity of the Most Sacred Heart of Jesus falls 19 days after Pentecost, on a Friday. The devotion to the Sacred Heart is one of the most widely practiced and well-known Roman Catholic devotions, taking Jesus Christ’s physical heart as the representation of his divine love for humanity.
According to the Gospel of John (19:33), when Jesus was dying on the cross “one of the soldiers pierced his side with a spear, and at once there came out blood and water.” The celebration of the Sacred Heart is associated with the physical wound (and the associated sacrifice), the “mystery” of both blood and water pouring from Christ’s chest, and the devotion God asks from humankind.
Pope Pius XII wrote about the Sacred Heart in his 1956 encyclical, Haurietis Aquas (On Devotion To The Sacred Heart):
“Devotion to the Sacred Heart of Jesus is devotion to Jesus Christ Himself, but in the particular ways of meditating on his interior life and on His threefold love: His divine love, His burning love that fed His human will, and His sensible love that affects His interior life.”