Exodus 12:3-4

3Speak to all the congregation of Israel, saying, ‘On the tenth of this month they are each one to take a 1lamb for themselves, according to their fathers’ households, a 2lamb for 3each household.

4Now if the household is too small for a 4lamb, then he and his neighbor nearest to his house are to take one according to the 5number of persons in them; according to 6what each man should eat, you are to 7divide the lamb.