40 Hence, We renew the urgent entreaty Wehave already made, to redouble zeal and perseverance, when addressing humblesupplications to our merciful God, so that the virtues whereby a Christian lifeis perfected may be reawakened. It is, however, urgent before all, that charity,which is the main foundation of the Christian life, and apart from which theother virtues exist not or remain barren, should be quickened and maintained.Therefore is it that the Apostle Paul, after having exhorted the Colossians toflee all vice and cultivate all virtue, adds: "Above all things, havecharity, which is the bond of perfection."(41) Yea, truly, charity is thebond of perfection, for it binds intimately to God those whom it has embracedand with loving tenderness, causes them to draw their life from God, to act withGod, to refer all to God. Howbeit, the love of God should not be severed fromthe love of our neighbour, since men have a share in the infinite goodness ofGod and bear in themselves the impress of His image and likeness. "Thiscommandment we have from God, that he who loveth God, love also hisbrother."(42) "If any man say I love God, and he hateth his brother,he is a liar."(43) And this commandment concerning charity its divineproclaimer styled new, not in the sense that a previous law, or even natureitself, had not enjoined that men should love one another, but because theChristian precept of loving each other in that manner was truly new, and quiteunheard of in the memory of man. For, that love with which Jesus Christ isbeloved by His Father and with which He Himself loves men, He obtained for Hisdisciples and followers that they might be of one heart and of one mind in Himby charity, as He Himself and His Father are one by their nature.
Source: Sapientiae Christianae (Vatican.va)