Korach confronted Moshe's leadership in a seemingly roundabout
fashion. He asked Moshe two contrived Halachik questions:
Does a Talis entirely dyed in Techeles - (a special blue dye) require Tzitzit?
Does a house filled with Sefarim (books) require a Mezuzah?
Moshe answered that in both cases the obligation is to follow the
commandment of Hashem, and put Tzitzit on a four cornered garment,
regardless of its color, and affix a Mezuzah to any doorway requiring
one, regardless of how many Sefarim the room contains.