Deuteronomy 16:3

‘And they shall eat the flesh that night, roasted with fire, and they shall eat it with unleavened bread and bitter herbs.

‘Seven days you shall eat unleavened bread, but on the first day you shall remove leaven from your houses; for whoever eats anything leavened from the first day until the seventh day, that person shall be cut off from Israel.

‘You shall also keep the Feast of Unleavened Bread, for on this very day I brought your hosts out of the land of Egypt; therefore you shall keep this day throughout your generations as a perpetual statute.

And Moses said to the people, “Remember this day in which you went out from Egypt, from the house of slavery; for by a strong hand Yahweh brought you out from this place. And nothing leavened shall be eaten.

‘Then on the fifteenth day of the same month there is the Feast of Unleavened Bread to Yahweh; for seven days you shall eat unleavened bread.

‘Then on the fourteenth day of the first month shall be the Passover of Yahweh.

‘And on the fifteenth day of this month shall be a feast; unleavened bread shall be eaten for seven days.

“Only keep yourself and keep your soul very carefully, lest you forget the things which your eyes have seen and lest they depart from your heart all the days of your life. But make them known to your sons and to your grandsons.

Then the king commanded all the people saying, “Celebrate the Passover to Yahweh your God as it is written in this book of the covenant.”

But you will not go out in haste, Nor will you go as those who flee; For Yahweh will go before you, And the God of Israel will be your rear guard.

And His parents would go to Jerusalem every year at the Feast of the Passover.

And the Passover of the Jews was near, and Jesus went up to Jerusalem.

Therefore let us celebrate the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth.