In the English dub of the eighteenth episode of InuYasha, Miroku uses this excuse to try to get out of having to face a demon. This is one of the examples of the trope doubling as Blatant Lies, since Miroku is a Buddhist monk whose job involves exorcising demons.
Miroku: If the demon is truly big, then we are no match for it. It's irrational. It's impossible. It's against my religion. Inu-Yasha: You oughtta be arrested.
In season two of Black Lagoon, two bounty hunters are shown drinking milk at a bar. When asked why, one replies that drinking alcohol is against his religion. The other just doesn't like the taste of it.
In Naruto, the very religious Hidan of the Akatsuki refers to this quite often. According to his cult-religion of Jashinism, it is a sin to leave a foe/enemy/victim alive; they must be defeated and slaughtered in the most painful, blood-gushingest way possible. Hidan also calls on Kakuzu when they have to break into a temple, saying that it goes against his beliefs (probably because even if someone is crazy like him, you still don't invade or desecrate other peoples' houses of worship). And he also has a problem with Kakuzu's covetousness of money, because greed is probably also a misdemeanor to Jashin. Weird values, if you ask me...
One Calvin And Hobbes strip has Calvin jotting down in his quiz that he couldn't answer a question because it's against his religion (see the page pic).
He's also a "math atheist" and refuses to do his homework because he cannot accept "on faith" that combining 2 and 2 makes 4 — and in the public schools, no less.
In The DCU, a member of the Green Lantern Corps took a vow to never leave her planet as part of her religion. Forced to go against this vow during the Sinestro War, she's since returned to her planet and refuses to leave no matter what. Her church, however, has yet to welcome her back. Her sector partner is an atheist and has petitioned many times for a new partner.
Another Dilbert strip has Dilbert's co-worker refusing to go out with him over religious differences. When Dilbert offers to change his religion, he discovers that there is an entire religion based on 'not dating Dilbert'.
Dogbert: Where do you think I go every Sunday?
In Twisted Toyfare Theater, The Thing finds out that he is Jewish by claiming that he cannot work on the Sabbath. Mr. Fantastic checks with his parents to find out that he actually is Jewish.
Get Fuzzy has a recurring joke where Bucky Katt uses this excuse. His owner then asks what Bucky's religion is. No points for guessing why Bucky won't tell him...
Robin Hood: Prince of Thieves featured Azeem, a Muslim who is forbidden by his faith from drinking alcohol. Friar Tuck doesn't have this limitation.
Friar Tuck: Let us open a bottle and do our best to save each other's souls. Azeem: Alas, I am not permitted. Friar Tuck: Fine then, you talk, I'll drink.
Lydia in Beetlejuice only gets a C on a science test since she refuses to dissect a frog, citing this reason.
The Big Lebowski has Jewish convert Walter, who initially refuses to drive to meet The Dude on Friday night because of the sabbath. The Dude reminds him that he was raised Polish Catholic and that he only converted to Judaism for his ex-wife, and Walter's a bit peeved by the implication that he should abandon his religion just because his wife left him.
In the Discworld book Thief of Time, the Auditors are disguised as humans, and avoid being forced to drink tea (where things like eating are harmful to them [it's a long story]) with this trope. The Auditors have noted that people will justify the most extreme behavior on the same basis, so by comparison refusing to drink tea shouldn't raise any eyebrows.
Moist von Lipwig uses it in Going Postal to avoid getting his picture taken, out of fear his un-memorable appearance, and through it the secret of his criminal past, won't survive a picture. Making Money proves him right.
In the Assassins' Guild Yearbook, a long list of loophole-filling rules to prevent any attempt by students to have a pet crocodile is eventually forced to concede that none of these rules apply to worshipers of Offler the Crocodile God. Then they add a rule that any student claiming Offlerism will be quizzed on the subject, because religion is not a joking matter. Then they have to acknowledge that, to worshippers of Nog-Humpty the Custard God, it is a joking matter.
Subverted with Mr. Dorfl. Normally golems like him take one day off a month because it is a "holy day", although they work 24/7 all other times. After gaining his freedom, Dorfl becomes an atheist and gives up this practice because he has decided that "either all days are holy or none are".
McCoy: You see, ma'am, these two gentlemen already have a dictator, it's against Mr. Sulu's religion... and I'm a Democrat.
In Spock - Messiah! by Theodore R. Cogswell and Charles A. Spano, Jr., the landing party are offered some very suspicious-looking stew which they turn down with the claim that they are religiously forbidden to eat meat on whatever day it currently is.
In Island In The Sea Of Time, one of the protagonists won't prostrate himself before the ruler of Mesopotamia because "it is against our custom, and the law of our god." Possibly a Shout Out to the Book of Daniel — the speaker is Jewish.
In Everworld, April, whose Catholicism is regularly mentioned, refuses to make a sacrifice to the Physical Gods of Everworld-Africa. In an interesting twist, atheistic Jalil joins her protest on the same logic. (Eventually, David and Christopher side with them, though more on the grounds of "screw these guys trying to tell us what to do" than anything.) Senna is disgusted by all of them, but more because they are putting Honor Before Reason than anything. (She, after all, wants toreplacethe gods.)
In The Thin Blue Line, someone gets sick in Fowler's hat, and Fowler absentmindedly puts it on. When his superior shows up and want to know why Fowler isn't taking his hat off in respect, he claims to be a Sihk who is forbidden to bare his head.
The Police Procedural nowadays often run into various religious groups who want to have a non-cut-up-body for burial. Depending on the religion and which AnviliciousAuthor Tract the writer wants to give this time, results will vary.
In Real Life, medical examiners promise to do a "minimally invasive" autopsy in murder cases — which means of course that they do a complete and full autopsy, only making sure that fluids aren't spilled. This is understood not just by MEs but also by rabbis, since letting a murderer get away with a crime is always considered more of a problem than a respectful autopsy.
A variant appears in Law & Order: Special Victims Unit. A suspect in a number of rape/murders claims he's a Jehovah's Witness, and so the court cannot compel him to give blood for a DNA sample. This is circumvented when a brother of one of the victims attacks him, and he bites the brother during the fight. The saliva on the bite was "given voluntarily", so it can be legally used for the sample.
This seems more like Hollywood Law, actually-suspects have blood samples taken under court order routinely, and objecting "against my religion" is unlikely to stop it from happening.
The Mormon candidate for fellowship on House cited this as a reason not to drink alcohol for an unusual diagnosis procedure,note A liver stress test, if you must know but House convinced him it was necessary and he did it anyway.
In Keeping Up Appearances, (something happens or is said) prompting Onslow to state that having breakfast (in bed?) isn't against his religion. When asked what is, his wife jokes, "Getting (up? out of bed?) before (insert time here)!"
Oz. Muslim inmate Kareem Said rejects Smug Snake Governor Devlin's politically-motivated pardon on live television by saying: "According to my religion, there are some things I am not allowed to swallow!"
One episode from the first season involved Franklin trying to save a boy with a surgical procedure that's against his species' religion, over his parents' refusal. They are entirely sincere in their beliefs, and when Franklin goes behind their back to perform the surgery, they kill the child, sincerely believing the child to no longer have a soul as a result.
In more lighthearted examples, Ivonova ends up having a discussion with her family rabbi about whether or not an alien dish called treel is kosher (Eventual ruling: It's not mentioned by name in the Bible, so it's probably OK). Ivonova herself does not appear to keep kosher, seeing as her only objection to Marcus using his contacts in the Rangers to provide her with bacon and eggs (Foods which are apparently hard to get on space stations) was that Sheridan and Garibaldi spent that breakfast staring at her plate and drooling.
In The Nanny, Fran comes up with fake Jewish holidays to get out of work, and she says she did that in school as well.
JAG: In the season nine episode “Posse Comitatus”, Bud investigates a Navy reservist physician who suddenly claims conscientious objector status when called on serve in Iraq because he became a Quaker. When Bud informs him that after separation his medical practice would at the same time also lose the military health plan affiliation, he backs down.
Arles: One time we raised so much hell in Houston I claimed to be an Episcopalian! Bertha: What was that like? Arles: I don't remember. By the time I came to I was back in Tuna feeling like a Baptist again!
Mr. Welch has been told with absolute certainty that Druids are not against his religion.
In the 2009 Christmas Special of Red vs. Blue, Grif claims to have joined every single religion in the world. That way, he can refuse to do anything, since, according to him, every day of the week is at least one religion's holy day of rest (except for Monday, curiously).
In one Teen Girl Squad episode, Cheerleader claims that sweating is against several of her religions.
In the Beavis And Butthead episode "Dumb Design", the boys use this excuse first to get out of learning evolution, and later to get out of math and P.E. class.
In Futurama, Bender tries to get out of doing work by pretending robot holidays such as "Robonukkah" prevent him from working.
Hermes mentions that the Planet Express corporation respects Bender's religious freedom to the extent the law requires, but he'd already spent all his allotted days off for Robamadan and Robanzaa.
Cody: Oh man, I can't believe I have to take an exam on... Shhh...abbat. Jessie: Cody... you're not Jewish. Cody: That's not the point!
An episode of Roger Ramjet has Roger coming to the aid of a stand-up comic. Roger is about to deliver a smackdown to Noodles Romanoff and his gang, and the stand-up comic says he'd like to join Roger but it's against his religion: he's a devout coward.
For many, this excuse is abused where something technically is against their religion, but they wouldn't be following that stricture (every religion has a few rules that only the real diehards pay attention to) if they didn't dislike the thing anyway.
Example: A Muslim, Buddhist, Baptist, or what-have-you who has in fact had a drink before and didn't like it might use "it's against my religion to drink" to avoid drinking in social settings, although s/he hadn't had any compunctions about it before.
Conscientious Objectors will do this in Real Life as their reasons not to fight in wars.
Not ALL of them (there are non-religious pacifists) but the ones claiming religious reasons get their status accepted more easily.
It doesn't necessarily stop them from going to war either. Some of the most heroic medics in history have been conscientious objectors.
Alvin York, probably the most famous American World War I war hero, was himself a conscientous objector.
Religiously motivated pacifism in general: Martin Luther King Jr. and Gandhi both saw violence against their oppressors as immoral for religious reasons, even in retaliation.
Jack Thompson used this excuse during his disbarment proceedings. The judges didn't fall for it.
There's a story in which a couple of Muslim diplomats met with Vlad Tepes (Yes, that one), refusing to remove their turbans. They refused to take off their hats because they were only required to do so in the presence of the Sultan. Vlad was a vassal of the Sultan by force, so this was a Take That, basically stating "Even though you are the most powerful man in the land we are currently in, you are lowly and deserve none of our respect." Unfortunately for the two of them, due to trying to pull a country with a nonexistent economy to a standing position, the constant threat of war from the Ottoman Empire, the raiding of border towns by Hungary, a staggeringly high crime rate, and the intrigues and plots from unwilling boyars and their crazy family clans, Vlad understandably had a bit of a Berserk Button when it came to respect.
Any Discordian can claim ANYTHING is against their religion, by virtue of being a Pope. Unfortunately, since everyone is also a Pope, you'll be promptly excommunicated.
The entire church (a.k.a. human race) was excommunicated within the first few days of the religion.
Fortunately, they can all de-excommunicate themselves. Unless that would be against their religion.
It is generally known that observant Jews may not eat pork, rabbit, shellfish, etc. What is less well known is that very observant Jews may not wear garments made from mixed fibers because of a Biblical instruction to refrain from wearing a certain kind of cloth made from flax and wool. And those who adhere very strictly to the dietary laws cannot eat anything made in a non-kosher kitchen (which means, among other things, entirely separate sets of cookware, dinnerware, and sinks for meat and for dairy).
This could possibly explain any Jewish vegetarians.
Among the Reform and Reconstructionist, perhaps. The Orthodox, and to a lesser extent the Conservatives, would remind you that in Temple times, there were animal sacrifices, and to this day, an animal bone is part of the Passover service.
Members of the LDS Church (Mormons) are famous for refraining from smoking and drinking alcohol, coffee, tea, and sometimes even caffeine of any kind. This is often used in media to mark a character as a Mormon. This comes from a piece of Mormon scripture popularly called the "Word of Wisdom", which also advises to use meat sparingly and the consumption of fruits, herbs, and grains. It is considered important enough that following it is a prerequisite for membership and for participation in several programs.
Jehovah's Witnesses refusal to accept blood transfusions gains occasional notoriety and provides fuel for Medical Dramas.
They also do not celebrate birthdays, nor do they pledge allegiance.
After becoming a born-again Christian, Shawn Michaels would tread carefully when he was part of the WWE's more risque skits. Sometimes they would have fun with this... Triple H blindfolding him before bringing out cheerleaders, being distracted away from girls, reluctantly going through the women's locker room and Eric Bischoff mocking his refusal to do stuff like Katie Vick as against his religion.
Most Muslims are excused from social dance lessons in schools on the grounds that one should not get that close to a member of the opposite sex with whom you are not betrothed.
Hindus famously do not eat beef. Some of them are total vegetarians.
There are also some extremely devout Hindu who don't do cow's milk or dairy for the same reason. This isn't quite as common as refusing beef, through, as milk, yogurt, and butter—particularly the clarified butter known as ghee—are pillars of Indian cuisine and (more to the point) are actually used in Hindu festivals (for instance, the oil in the lamps of Diwali is traditionally ghee).
U.S. employment discrimination law more or less requires an employer to believe (or at least act like they believe) an employee who says something is against his or her religion. Even if the employer has never heard of the prohibition. Even if the employer has never heard of the religion. note The employer is not necessarily required to care; they just can't question it without a specific reason for doubt
Inverted in the case of many atheists and agnostics, who may refuse to do something like say the words "under God" in the American pledge of allegiance - not because it's against their religion, as they may not have any, but because they feel it is a part of someone else's.
In most schools in the United States, there are mandatory sex education classes. All are required to allow a student to decline them on religious grounds and spend the time in an alternative activity.
A man in Austria won the right to wear a spaghetti strainer on his head in his drivers licence photo because of his religious beliefs.
The person is known as Niko Alm and this was more of a publicity stunt. He protested against the "privilege" of Religious people to get their photos taken with various forms of headgear. He got this allowed in the end, because the spaghetti strainer didn't obstruct his face and not based on his belief.
Commonly attempted by younger kids during Lent, the Christian preparation for Easter, as the tradition is to give something up so you suffer some. Some try to give up vegetables, homework, or school.
Seventh-day Adventists are known for abstaining from secular activities on the Sabbath (i.e. from sunset Friday to sunset Saturday) according to the instruction given in the fourth of the Ten Commandments in Exodus 20 (specifically, verses 8-11) and the description of the transition of days from sunset to sunset in Genesis 1. Many also abstain from meat and alcoholic drinks due to this trope; SDA members who do eat meat refrain from eating meats listed as forbidden in Leviticus 11 (particularly pork or pork-made products).