Exodus 12:3-6

3Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb, according to their fathers’ houses, a lamb for a household:

4and if the household be too little for a lamb, then shall he and his neighbor next unto his house take one according to the number of the souls; according to every man’s eating ye shall make your count for the lamb.

5Your lamb shall be without blemish, a male a year old: ye shall take it from the sheep, or from the goats:

6and ye shall keep it until the fourteenth day of the same month; and the whole assembly of the congregation of Israel shall kill it at even.