Parshat Korach

Korach took 250 magistrates... and dressed them in garments that were wholly of blue wool. They stood before Moses and asked him: "If a garment is made entirely of blue wool, what is the law as regarding the obligation of tzitzit?" Moses answered them: "It is obligated." They began to laugh at him, saying: "If a garment of another sort is absolved by a single thread of blue wool, this garment, composed wholly of blue wool, cannot absolve itself?"

Korach further challenged Moses: "If a house is full of Torah scrolls, does it need a mezuzah on its doorpost?" Replied Moses, "It is obligated." Said Korach: "The entire Torah, consisting of 275 chapters, does not absolve this house, and the [two] chapters in the mezuzah absolve it? G-d did not command you these laws -- you have invented them yourself."

(Midrash Rabbah)