The Lord spoke to Moses and Aaron in Egypt: 12
"This month is to be the first month of the year for you.
Give these instructions to the whole community of Israel: On the tenth day of this month each man must choose either a lamb or a young goat for his household.
If his family is too small to eat a whole animal, he and his next-door neighbor may share an animal, in proportion to the number of people and the amount that each person can eat.
You may choose either a sheep or a goat, but it must be a one-year-old male without any defects.
Then, on the evening of the fourteenth day of the month, the whole community of Israel will kill the animals.