"suppose that there are some rich people who, though they are not in the habit of helping the poor in the Church [(pauperes Ecclesiae)] with their largess, keep at any rate the commandments of God and figure that from among the various meritorious activities of faith they are lacking but one virtue—and it is therefore a slight fault. Yet this one virtue happens to be so important [(et inter diversa fidei et probitatis merita, veniabiliter sibi aestimant unam deesse virtutem. Verum haec tanta est)] that without it the others cannot be of any avail.
"Be any full of faith, chaste, sober, and adorned with other noteworthy habits, yet if they are not merciful, they do not deserve mercy. For the Lord says, 'Blessed are the merciful, for God will have mercy on them.' When the Son of Man will come in his majesty and sit on the throne of glory, when all nations have been gathered together, the good and the bad will be separated. What will those who are destined to stand on the right be praised for if not the benevolent works and charitable services that Jesus Christ will consider as rendered unto himself? . . . What accusations will be made against those on the left if not neglect of love, inhuman hardness, and denying compassion to the poor?
"As if those on the right would not have other virtues, those on the left other offenses! But at that great and ultimate judgment, the kindness of generosity or the ungodliness of avarice receives an extremely high value. Despite perpetuating all manner of the greatest crimes, some are accepted into heaven on account of that one good [(unum bonum)]. Despite possessing the fullness of all virtues, others are cast into eternal fire on account of that one evil [(unum malum)].
"Let none then, dearly beloved, flatter themselves about any merits due to living a good life if they lack charitable works. Nor should any be complacent about the purity of their bodies if they have not 'been cleansed' at all by the purification 'of alms.' 'Alms' wipe away 'sins,' do away with 'death,' and extinguish the punishment of eternal fire. But those who will have been found empty of its fruit will be strangers to lenience from the one who gives recompense—as Solomon says: 'Whoever stop up their ears so as not to hear the enfeebled will themselves call upon the Lord and likewise find no one to hear them.' So Tobias as well, instructing his son in the demands of religion, says: 'Give alms from your possessions and do not turn your face away from any of the poor. That way, the face of God will not be turned away from you either.'
"This virtue causes all other virtues to be worth something. It gives life even to faith itself—'by which the just live' and which is called 'dead without works'—by mingling with it. While faith provides the basis for works, the strength of faith comes out only in works."
Pope Leo the Great, Sermon 10.2-3 (November 444). St. Leo the Great: Sermons, trans. Freeland & Conway, FC 93 (Washington, DC: The Catholic University of America Press, 1996), 44-45 (42-46). Latin: CCEL 138, 41-43 (39-44); SC 49 bis, pp. 52-55 (48-57); PL 54, cols. 165 ff.