For seven days you are to eat bread made without yeast. On the first day remove the yeast from your houses, for whoever eats anything with yeast in it from the first day through the seventh must be cut off from Israel.
-Exodus 12:15-

Leavened bread became a symbol of what is allowed to stand around. It signified staleness and deadening routine; getting rid of it became the symbol of freshness and growth. Since Passover occurs in the spring, the total cleaning of the house to eliminate leaven was easily expanded to a comprehensive spring-cleaning. Throwing out the accumulated staleness and the dead hand of winter, cleaning the house became a psychological backdrop for reenacting emancipation. Housecleaning became part of the cosmic process.
-Irving Greenberg-