It's the darkest hour. An important struggle is in the balance. And the hero's mighty blade would surely save the day ... but he promised his mother he would never unsheathe his weapon again.
Anguished and unsure, he watches the fight grow more and more hopeless. And then, just when all seems lost, he strides forward (possibly with a "Sorry, Mom"), draws his sword and turns the tide.
You broke your word. And a good thing, too.
Unlike the Oath Breaker, no serious stigma will attach to a hero who exercises this trope, no matter how heartfelt the principles involved are. This can be a Broken Aesop if the lesson is "Promises should only be kept when they are convenient." On the other hand, the more family-friendly version might read "Hasty promises and poorly thought-out commitments are no excuse for not doing the right thing."
A possible consequence of I Gave My Word; indicates that a hero has abandoned Honor Before Reason. Violence Really Is The Answer is often (though not always) learned as a result.
- In "High Noon," the hero's wife Amy (Grace Kelly) is a Quaker sworn to pacifism. But when her husband Will chooses to fight a criminal bent on revenge rather than flee, she saves Will's life by shooting his foe.
- In Terry Pratchett's "Unseen Academicals," Trev Likely, the son of a brilliant football player who died during a match, has promised his mother he will never play the game himself. But when the wizards of Unseen University desperately need one more player to pull out their high-stakes game (and with his true love watching), Trev swallows his fears and joins the game. A partial subversion in that Trev proves to be terrible at handling a football ... until it's replaced, via a bit of Loophole Abuse, with the tin can he's an expert at kicking instead.
- "Coward of the County," by Kenny Rogers, depicts a man named Tommy who promised his father that he would walk away from trouble and never fight. But when his girl is raped by a gang of outlaws, Tommy locks himself in a bar with them and clobbers every last one of them.
- Rigby and Mordecai of "Regular Show" trap themselves in a no-holds barred stick hockey game against the murderous player Chong, only to be rescued by the skills of their overbearing boss Benson. Benson, it's revealed, is a former master of the game who swore never to play it again after Chong killed his apprentice during a match.