The image behind “wolf in sheep’s clothing” is older than its familiar English wording: a predator hides among harmless animals, and danger wears the appearance of innocence. The earliest well-known surviving version appears in Matthew 7:15, where Jesus warns against false prophets who “come to you in sheep’s clothing, but inwardly they are ravening wolves.” The Gospel is generally dated to the late first century, though the precise date—and whether the image circulated earlier in speech or story—cannot be pinned down.
In Matthew, the warning is about religious teachers whose outward appearance conceals their character. The next lines advise judging them by their “fruits,” or actions. The metaphor thus begins as a caution about spiritual deception, not simply a label for any unpleasant person. Its force comes from the contrast: sheep suggest vulnerability and trust, while the wolf represents a hidden threat.
A popular account says the phrase originated in Aesop’s Fables centuries before the Bible. A wolf-in-disguise story is indeed associated with the Aesopic tradition, but that association does not establish when the tale was first told or prove that Aesop created it. The fables circulated orally and survive in collections assembled at different times, so the story’s supposed ancient authorship is not firm evidence for the phrase’s precise origin. The biblical passage is an early, identifiable witness to the image, not proof that no one used it before.
As biblical language entered English, the image became especially familiar through translations such as the King James Bible, published in 1611. Over time, its meaning broadened from false religious teachers to anyone—or any group—whose harmless or respectable exterior masks harmful intentions. “The charming new investor seemed like a wolf in sheep’s clothing once the fine print came to light.” “The company’s friendly promises were a wolf in sheep’s clothing, hiding steep fees.”
The phrase endures because it turns an abstract warning about deception into a vivid scene: the disguise looks safe, but the threat remains.