Exodus 12:5-7

Your lamb shall be without blemish, a male a year old. You may take it from the sheep or from the goats, and you shall keep it until the fourteenth day of this month, when the whole assembly of the congregation of Israel shall kill their lambs at twilight. “Then they shall take some of the blood and put it on the two doorposts and the lintel of the houses in which they eat it.