Exodus 34:24-25

24I will chase the nations out of the land as you move in. I will give you more and more land to live in. Three times each year you must come to worship the Lord your God. When you do that, nobody will try to take your land for themselves.

25When you offer the blood of an animal to me as your sacrifice, do not also offer any bread with yeast in it. When you kill a lamb for the Passover sacrifice, do not keep any of the meat until the next morning.