Cardinal Manning distinguishes sins of commission from sins of omission: “The first was the sin of doing evil; the last, the sin of leaving good undone.”
“Let me suppose a soul created in the likeness of God, and committing no sin, but bearing no fruit. This is precisely the state described in the parable of the barren fig-tree. The tree was alive, the root strong and in the ground, the branches were covered with leaves; but when, year after year, the fruit was sought, none was to be found. This is a parable and description of a soul, alive indeed, but not fulfilling the end of its creation. And for what end was the soul created? To know, to love, to serve, to worship, and to be made like to God.”
“We are bound by three obligations to glorify God by fulfilling the end of our creation. First, by the law of our creation itself. We were created to glorify Him by a life of obedience. . . . If the firmament were turned into darkness, and the earth into desolation, it would not fulfil the end for which it was made; and so, too, with the soul that does not glorify God.”
Secondly, “we are bound to glorify God by a direct commandment, and that direct commandment is written in the Decalogue and in the two precepts of charity: ‘Thou shalt love the Lord thy God with thy whole heart, with thy whole soul, with thy whole mind, with thy whole strength, and thy neighbour as thyself” (Mt 22:37, 39).”
A third obligation is “the law of liberty—the law of love, of gratitude, and of generous freedom, which is written by the Holy Ghost on the heart of all those who, being born again in Baptism, are united to our Lord and Saviour Jesus Christ by the bond of charity.”
“Sins of omission are against either the law of our creation, or the law of the two precepts of charity, or against the law of liberty. If we leave undone the good or the duties to which we are bound by those obligations, we commit sins of omission.”
Quotations from Henry Edward Manning, Sin and Its Consequences, 2d ed. (London: Burns and Oates, 1874).