This phrase originates from Talmudic discussions, particularly within the context of halachic (Jewish legal) rulings. The concept is that if a scholar or judge makes a mistake in a ruling that contradicts a clear teaching from the Mishnah—a central text of Jewish oral law—they are obligated to correct their error and retract their previous decision.

The Mishnah is a fundamental and authoritative source in Jewish law, so an error that goes against it cannot stand.