A Topic of Moral Theology
The sin of omission
The sin of omission, as treated in Billuart (On the Nature of Sin).
The works themselves ask 4 questions under this heading — see them together with their answers.
In the index as Imputability of the human act · Omission of an act · Omission, sin of · Sin
In the manuals
Read the manuals side by side → — each work's whole treatment in its own column
Summa Theologiae Moralis
Vol. I, General Moral Theology, Treatise: On Sins in General, First Part: On Sin Accordi…, First Question: On the Ess…, Article II: On the Sin of Omission Negatively Voluntary, nn. ¶1, 419, 420 & 421 (7 passages — hover a number to read it)
Summa Summae S. Thomae (Billuart)
Billuart, Summa Summae, Tomus II. On the Prima Sec…, On Sins, On the Nature of Sin, On the sin of omission, nn. 1–29 (29 passages)
Treated under the broader heading Sin — Noldin, Summa of Moral Theology · Slater, Manual of Moral Theology · Wouters, Manual of Moral Theology · McHugh–Callan, Moral Theology · Bucceroni, Institutions of Moral Theology · Bucceroni, Moral Enchiridion (4th ed., 1905) · Bucceroni, Cases of Conscience · Gury-Ballerini, Compendium of Moral Theology (8th ed., 1884) · Tanquerey · Vermeersch, On Forbidden Books · Koch–Preuss · Prümmer, Manuale Theologiae Moralis · Marc, Institutiones Morales · Konings, Theologia Moralis and 4 more — these works do not divide the matter as finely as we do here, so their treatment stands one heading up (ed.)