Deuteronomy 16:7

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

‘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.

‘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.

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.”