Exodus 12

5 Your lamb must be a year-old male without any defects, and you can take it either from the sheep or the goats.

6 Keep it until the fourteenth day of the month, when all the Israelites will slaughter the animals after sunset and before it gets dark. 7 They are to take some of the blood and put it on the sides and tops of the doorframes of the houses where they have the meal.