Exodus 13:5

When the Lord shall bring you into the land, thou shalt keep this service Until then they were not obliged to keep the passover, without a particular command from God. There shall no leavened bread be seen in all thy quarters Accordingly the Jews' usage was, before the feast of the passover, to cast all the leavened bread out of their houses; either they burned it, or buried it, or broke it small, and threw it into the wind; they searched diligently with lighted candles in all the corners of their houses, lest any leaven should remain. The strictness enjoined in this matter was designed, 1st, To make the feast the more solemn, and consequently the more taken notice of by the children, who would ask, Why is so much ado made? 2d, To teach us how solicitous we should be to put away from us all sin.