Exodus 12:3-4

Speak to all the congregation of Israel, saying, ‘On the tenth of this month they are each one to take a lamb for themselves, according to their fathers’ households, a lamb for each household. Now if the household is too small for a lamb, then he and his neighbor nearest to his house are to take one according to the number of persons in them; according to what each man should eat, you are to divide the lamb.