123 Finally, moved by an earnest desire to set strong bulwarks against the wicked designs of those who hate God and the Church and, at the same time, to lead men back again, in their private and public life, to a love of God and their neighbor, We do not hesitate to declare that devotion to the Sacred Heart of Jesus is the most effective school of the love of God; the love of God, We say, which must be the foundation on which to build the kingdom of God in the hearts of individuals, families, and nations, as that same predecessor of pious memory wisely reminds us: "The reign of Jesus Christ takes its strength and form from divine love: to love with holiness and order is its foundation and its perfection. From it these must flow: to perform duties without blame; to take away nothing of another's right; to guide the lower human affairs by heavenly principles; to give the love of God precedence over all other creatures."(124)
Source: Haurietis Aquas (Vatican.va)