In some circumstances, drawing a weapon is taken very seriously. So seriously that some warriors are not allowed to sheath their weapon until they have used it to draw blood. Usually the intent is to wet the blade with the blood of one's enemies, but if none are available, the warrior may substitute his own blood to honor the letter of the rule. In such cases, the warrior will usually cut his hand with the blade.
The reason for the rule can vary widely per example. Some warriors may feel honor-bound to carry through the threat that a drawn weapon implies. The rule might serve to limit pointless aggression or empty threats by forcing the warrior to only draw in life-or-death circumstances. Maybe the weapon is treated as a living thing that must have its bloodlust sated. Whatever the reason, the weapon bearer will usually be very reluctant to transgress the rule.
In real life, this trope is sometimes found in myths about various warrior cultures, but they are always untrue: real-life Proud Warrior Race Guys know that weapons need to be drawn all the time for maintenance and practice, and cutting yourself deliberately out of such a superstition (especially in times of poorer medical knowledge) is a silly reason to risk sepsis. Where there is any element of Truth in Television, it's usually a heavily corrupted version of, "Don't pull your weapon out and wave it around unless you intend to use it".
- In an issue of The Tick, Paul the Samurai has an overly dramatic monologue to himself, which he ends by pulling out his sword and striking a pose. He then remembers that his sword can only be sheathed when it has tasted blood. He then looks at his hand, which is covered in band-aids. Apparently, it was a bad habit of his.
- Kin-Slayer in Chronicles of the Kencyrath is portrayed as a weapon which doesn't want to be put in the scabbard without having killed someone first.
- Dune: The Fremen consider it a very grave offense to re-sheathe a crysknife without drawing blood. Justified by more than just culture in this case: crysknives are made from the teeth of dead sandworms, and human blood contains chemicals that stave off decay. It helps that the Fremen have quick-congealing blood, and that a quick cut across one's arm counts as drawing blood.
- In The Legends of Ethshar novel The Misenchanted Sword, the eponymous sword literally could not be resheathed, or even put down, until it had been used to kill somebody.
- The Alchemist: While travelling with a caravan, Santiago gets a premonition that they're going to be attacked. He informs the chief, who tells him that they'll make defensive preparations, but if he was wrong they'll kill him, since apparently "blood must be shed once weapons are drawn". Fortunately (for him), he was right.
- In Kushiel's Legacy, members of the Cassiline Brotherhood, an order of Warrior Monks who act as elite bodyguards, carry a two-handed sword and dual daggers. The daggers are fair game, but Cassilines are forbidden to draw their swords in the field except to kill in defense of their charge. Phedre's bodyguard/lover Joscelin Verreuil holds to this even after being expelled from the order, informing General Barquiel l'Envers of it in Kushiel's Chosen after the latter challenges him to some nonlethal sparring. (Joscelin defeats the sword-wielding general with his daggers.)
- Kelemvor Lyonsbane's Sins of Our Fathers curse in the Avatar Series of Forgotten Realms novels is an unusual variant that doesn't actually involve a weapon. Any time the curse triggers, he turns into a giant were-panther and can't change back into a human until he kills someone.
- In The Lord of the Rings, shortly after the Battle of the Pelennor Fields, Aragorn unsheathes his sword Anduril and boasts, "You shall not be sheathed again until the last battle is fought." Considering that the final battle of the War of the Ring isn't fought for another ten days, seven of which he spent on horseback, his arm must have been mighty sore by the time he sheathed it again.
- In The Heroes, this is the rule for the Father of Swords. Whirrun of Bligh will cut his hand if he has to in order to the sheath the sword without fighting. He doesn't like the rule, but he follows it.
- Babylon 5: The Narn have a special warrior's sword, K'tok, which tradition mandates cannot be re-sheathed until it has tasted blood. In one episode this trope was lampshaded, and later the proud warrior from the agrarian culture drew the sword for effect. He discreetly cut his palm before putting the sword away.
- In Battlestar Galactica (1978), there was a race called the Borellian Nomen. They had a warrior's code that said that if they drew their long knife, they would prefer suicide to seeing the knife resheathed unbloodied.
- Referenced in an episode of Magnum, P.I.. In the tag, Magnum's being a pain to Higgins, and mentions this trope in reference to Higgins unsheathing a katana. Then Higgins gets this crazy gleam in his eye and says "I know.".
- Norse Mythology:
- Prose Edda: King Högni's dwarf-made sword Dáinsleif "has to be the death of someone every time it is unsheathed." When Högni challenges King Hedin to battle because Hedin has abducted his daughter, Hedin wants to reconcile; Högni declines because he has already drawn Dáinsleif, and thus the spell has to be appeased.
- The Saga of Hervor and Heidrek: The sword Tyrfing "could never be held unsheathed without being the death of a man, and it always had to be sheathed with blood still warm upon it." This is told as a plain fact in the older version; in the younger version is is a curse laid on the sword by the dwarfs that made it. It is unclear how this spell works in practice, as Tyrfing is sheathed several times without anyone getting killed; while all wielders who do this come to a bad end, it is not obvious whether this is because of the curse.
- Hrolf Kraki's Saga: The sword left to Bodvar Bjarki by his father "could never be drawn without being the death of a man."
- Some tales suggest that the swords made by the Real Life swordsmith Sengo Muramasa are Evil Weapons that can only be sheathed once they have drawn blood (and aren't picky about where it comes from), and that they can drive their wielders mad with bloodlust.
- In 3.5e at least, there was a Dungeons & Dragons mechanic that was a quality of an intelligent weapon, that was almost word for word the laconic version of this trope.
- In Nomine supplement Superiors I: War and Honor. One of the oaths that can be sworn by a Malakite angel of Laurence is "I will not draw my sword unless I intend to kill someone".
- In Dark Heresy, a Feral Worlder character can have this as a superstition. As in, his/her weapon doesn't actually have this trait (hopefully) but s/he believes it does.
- KABAL (Knights and Berserkers and Legerdemain) Referee Guide. One possible type of magic weapon special ability was actually a drawback. If the wielder attempted to sheathe it before it had drawn blood, it would attack all nearby creatures as if it was a Dancing Sword until it had hit each of them once.
- It is rumored the Ba'al Verzi daggers in the Ravenloft setting cannot be sheathed before having killed someone.
- Mark of the Ninja has a variation of this. The ninja only uses his sword when he is guaranteed a kill. If the player messes up and enters open combat, the ninja relies purely on unarmed martial arts.
- The cursed swords in Muramasa: The Demon Blade cannot be sheathed until they have tasted blood. It there's no one around to kill, the swords will turn on their wielders.
- Team Fortress 2 has the Half-Zatoichi, a katana used by the Soldier and Demoman classes which can only be switched for another weapon without penalty if the user has gotten a kill with it or goes to a resupply cabinet. Otherwise, 50 HP is lost upon weapon switch, and cannot be switched at all if the loss would be lethal. Upon a kill it heals 50% of the player's base HP, and it's an instant One-Hit KO against another Half-Zatochi wielder.
- Halo: The Sangheili, a Proud Warrior Race, claim that no weapon should be drawn without intent of using it, or else it demands blood. In Halo Wars, though, the Arbiter Ripa 'Moramee draws his energy swords in the presence of one of the Prophets, a double blasphemy. It's a sign of his disrespectful attitude toward his own religion, and his high rank is the only reason the Prophets' Honor Guards don't kill him on the spot.
- In zOMG!, the Muramasa sword cannot be sheathed until it has drawn blood.
- In Gaia Online, the Muramasa sword cannot be sheathed until it has drawn blood.
- American Dad! "Best Little Horror House in Langley Falls": Once Steve fails to bring back Akiko from trick or treating before sundown like he promised, Toshi dons his Samurai costume and swears that his sword will taste blood. Steve manages to talk Toshi into not killing him and to stop being so overprotective. Instead, Toshi slaughters a bunch of Serial Killers set loose during the A plotline to satisfy the oath.
Toshi: (Subtitles) Once this Sword is drawn, it must taste blood.
- Although a popular legend states that a Gurkha "never sheathes his blade without first drawing blood" this is in fact untrue, and the kukri is most commonly employed as a multi-use utility tool rather like a machete. There is no requirement to prick yourself or anyone else before sheathing the blade. However there have been instances of Gurkhas slicing their fingers with it as a practical joke to impress outsiders with their ferocity. It's also been theorized that the "must taste blood" was something that annoyed Gurkhas started telling tourists, to make them stop asking to see the kukris.
- Many Sikhs carry a small steel knife known as a kirpan, as a reminder and a means to protect the innocent from harm. Periodically this has to be taken out and sharpened, but as the blade supposedly cannot be unsheathed unless it is to draw blood, the sharpener supposedly has to nick a thumb or finger with it before putting it away. This, too is a myth. In reality, while the kirpan is a holy symbol that should only be drawn either for maintenance, to defend oneself or another, or to cut the prasad (a religious offering of food), drawing blood is not necessary.
- Ditto samurai. While some Japanese folklore features the trope, e.g. the Hungry Weapon legend surrounding the swords forged by 16th century smith Muramasa Sengo, real-life samurai were as aware of the safety issues as the Gurkhas and Sikhs.
- This trope is often humorously applied to slipjoint pocketknives, as the springs that stabilize the blades in the open and closed positions have the unfortunate side effect of making it very easy to accidentally cut yourself while closing the blade.