Leviticus 23:4-8
Rules about the Passover Festival
4 There are also times that I have chosen for festivals. They are holy days when you must meet together to worship me. 5 The Passover Festival will be on the 14th day of the first month of each year. It will begin when the sun goes down on that day. It is a time to give honour to the Lord. 6 On the next day, the 15th day of the first month, the Festival of Flat Bread will begin, to give honour to the Lord. For seven days you must eat bread that has no yeast in it. 7 On the first of those seven days, you must all meet together to worship the Lord. You must not do your usual work. 8 For seven days you must offer sacrifices as a gift to the Lord. On the seventh day you must meet together again to worship the Lord. You must not do your usual work on that day.’
23:8When the Lord wanted to take his people out of Egypt, he told Israel's people to stay in their houses on their last night there. They had to put a mark on their doors with blood from a young sheep or a young goat. The Lord's angel killed the oldest son in the houses of the Egyptians. But he passed over the houses with blood around the doors. So the Lord saved the sons of the Israelites. That is why this is called the Passover Festival. See Exodus 12:12-20. 