101 The pierced heart of Christ embodies all God’s declarations of love present in the Scriptures. That love is no mere matter of words; rather, the open side of his Son is a source of life for those whom he loves, the fount that quenches the thirst of his people. As Saint John Paul II pointed out, “the essential elements of devotion [to the Sacred Heart] belong in a permanent fashion to the spirituality of the Church throughout her history; for since the beginning, the Church has looked to the heart of Christ pierced on the Cross”.
Source: Dilexit Nos (Vatican.va)