Exodus 12:3-5

Tell the whole community of Israel that on the tenth day of this month each man is to take a lamb for his family, one for each household. If any household is too small for a whole lamb, they must share one with their nearest neighbor, having taken into account the number of people there are. You are to determine the amount of lamb needed in accordance with what each person will eat. The animals you choose must be year-old males without defect, and you may take them from the sheep or the goats.