148 Devotion to the heart of Christ reappears in the spiritual journey of many saints, all quite different from each other; in every one of them, the devotion takes on new hues. Saint Vincent de Paul, for example, used to say that what God desires is the heart: “God asks primarily for our heart – our heart – and that is what counts. How is it that a man who has no wealth will have greater merit than someone who has great possessions that he gives up? Because the one who has nothing does it with greater love; and that is what God especially wants…” This means allowing one’s heart to be united to that of Christ. “What blessing should a Sister not hope for from God if she does her utmost to put her heart in the state of being united with the heart of our Lord!”
Source: Dilexit Nos (Vatican.va)