Sin of omission

In Catholic teaching, an omission is a failure to do something one can and ought to do. If an omission happens deliberately and freely, it is considered a sin.
The degree of guilt incurred by an omission is measured, like that attaching to sins of commission, by the dignity of the virtue and the magnitude of the precept to which the omission is opposed, as well as the amount of deliberation.
A person may be guilty of a sin of omission if he fails to do something which he is able to do and which he ought to do because he has put himself into a state or situation whereby he is unable to complete the action. For example, if a person chooses to become inebriated and is therefore unable to perform a necessary task, that person is responsible for that failure, even though that person is physically unable to perform the task because he or she knowingly put themselves into a state (drunkenness) where accomplishing the task was impossible.
Paul the Apostle refers to this sin directly when he states "For I do not do the good I want ..." (Romans ).
James the brother of Jesus more exactly defines this sin when he states, "Whoever knows the right thing to do and fails to do it, for him it is sin." (James )
"In the end, we will remember not the words of our enemies, but the silence of our friends." —Martin Luther King Jr.
Lie of omission.
In Catholicism, the ninth commandment is "Thou shalt not bear false witness against thy neighbour." This includes lies of omission, also known as exclusionary detailing or continuing a misrepresentation. In common parlance, a lie of omission may be referred to as "playing dumb."
In popular culture.
In the final episode of Seinfeld titled The Finale (Seinfeld), season 9 episodes 23 and 24, the characters are arrested on a duty to rescue violation. This law requires people to act as good Samaritans, and holds citizens legally liable for their failure to act.
In "The West Wing" TV series, season 3, episode 3 "Manchester: Part 2", Toby talks about President concealing his multiple sclerosis from the staff: "He didn't lie. It's what your people call a "sin of omission."
In "Burn Notice", Season 2, Episode 15 "Sins of Omission", Michael's ex-fiancée shows up needing help. In an argument about why he never talked about his almost-wife, Fiona dismisses Michael's answer with "sins of omission, Michael!"
In "Dexter", Season 6, Episode 8, "Sin of Omission", Dexter shows Travis Marshall the part of Bible about the sin of omission to convince Marshall to tell him where Professor Gellar (the doomsday killer) is.
In ‘Gossip Girl’ Season 4, Episode 12 Chuck Bass says to Lily Humphrey: “You’re familiar with the sin of omission?” when they discuss the sale of Bass Industries at an event.