13 The zeal of Catholics on behalf of the masses is especially praiseworthy because it is engaged in the very same field in which, under the benign inspiration of the Church the active industry of charity has always labored, adapting itself in all cases to the varying exigencies of the times. For the law of mutual charity perfects, as it were, the law of justice, not merely by giving each man his due and in not impeding him in the exercise of his rights, but also by befriending him, "not with the word alone, or the lips, but in deed and in truth";(6) being mindful of what Christ so lovingly said to His own: "A new commandment I give unto you, that you love one another, as I have loved you, that you love also one another. By this shall all men know that you are My disciples, if you have love one for the other."(7) This zeal in coming to the rescue of our fellow men should, of course, be solicitous, first for the eternal good of souls, but it must not neglect what is good and helpful for this life.
Source: Graves de Communi Re (Vatican.va)