Exodus 12:15 "But on the first day, you shall remove leaven from your houses"

This Positive Mitzvah is one of the commandments regarding the holiday of Pesach.

We are commanded to remove all leaven (Chametz) from our homes by the fourteenth day of the month of Nisan.

By removing the Chametz, we commemorate the story of Pesach when our ancestors were led out of Egypt without having any Chametz - leavened bread in their food supply for their journey.