79 A number of my Predecessors have spoken in various ways about the heart of Christ and exhorted us to unite ourselves to it. At the end of the nineteenth century, Leo XIII encouraged us to consecrate ourselves to the Sacred Heart, thus uniting our call to union with Christ and our wonder before the magnificence of his infinite love. Some thirty years later, Pius XI presented this devotion as a “summa” of the experience of Christian faith. Pius XII went on to declare that adoration of the Sacred Heart expresses in an outstanding way, as a sublime synthesis, the worship we owe to Jesus Christ.
Source: Dilexit Nos (Vatican.va)