Then the LORD said to Moses,
"Dedicate to me all the firstborn sons of Israel and every firstborn male animal. They are mine."
So Moses said to the people, "This is a day to remember forever -- the day you left Egypt, the place of your slavery. For the LORD has brought you out by his mighty power. (Remember, you are not to use any yeast.)
This day in early spring will be the anniversary of your exodus.
References for Exodus 13:4
You must celebrate this day when the LORD brings you into the land of the Canaanites, Hittites, Amorites, Hivites, and Jebusites. This is the land he swore to give your ancestors -- a land flowing with milk and honey.
For seven days you will eat only bread without yeast. Then on the seventh day, you will celebrate a great feast to the LORD.
Eat only bread without yeast during those seven days. In fact, there must be no yeast in your homes or anywhere within the borders of your land during this time."
"During these festival days each year, you must explain to your children why you are celebrating. Say to them, 'This is a celebration of what the LORD did for us when we left Egypt.'
This annual festival will be a visible reminder to you, like a mark branded on your hands or your forehead. Let it remind you always to keep the LORD's instructions in your minds and on your lips. After all, it was the LORD who rescued you from Egypt with great power."
"So celebrate this festival at the appointed time each year.
And remember these instructions when the LORD brings you into the land he swore to give your ancestors long ago, the land where the Canaanites are now living.
All firstborn sons and firstborn male animals must be presented to the LORD.
A firstborn male donkey may be redeemed from the LORD by presenting a lamb in its place. But if you decide not to make the exchange, the donkey must be killed by breaking its neck. However, you must redeem every firstborn son."
"And in the future, your children will ask you, 'What does all this mean?' Then you will tell them, 'With mighty power the LORD brought us out of Egypt from our slavery.
Pharaoh refused to let us go, so the LORD killed all the firstborn males throughout the land of Egypt, both people and animals. That is why we now offer all the firstborn males to the LORD -- except that the firstborn sons are always redeemed.'
Again I say, this ceremony will be like a mark branded on your hands or your forehead. It is a visible reminder that it was the LORD who brought you out of Egypt with great power."