100 From what We have so far explained, venerable brethren, it is clear that the faithful must seek from Scripture, tradition and the sacred liturgy as from a deep untainted source, the devotion to the Sacred Heart of Jesus if they desire to penetrate its inner nature and by piously meditating on it, receive the nourishment for the fostering and development of their religious fervor. If this devotion is constantly practiced with this knowledge and understanding, the souls of the faithful cannot but attain to the sweet knowledge of the love of Christ which is the perfection of Christian life as the Apostle, who knew this from personal experience, teaches: "For this cause I bow my knees to the Father of our Lord Jesus Christ. . . that He may grant you, according to the riches of His glory, to be strengthened by His Spirit with might unto the inward man; that Christ may dwell by faith in your hearts; that, being rooted and founded in charity. . .you may be able to know also the charity of Christ which surpasseth all knowledge, that you may be filled unto all the fullness of God."(101) The clearest image of this all-embracing fullness of God is the Heart of Christ Jesus Itself. We mean the fullness of mercy which is proper to the New Testament, in which "the goodness and kindness of God our Savior appeared,"(102) for "God sent not His Son into the world to judge the world, but that the world might be saved by Him."(103)
Source: Haurietis Aquas (Vatican.va)