Exodus 12:5-8

Your lamb shall be without blemish, a male of the first year. You may take it from the sheep or from the goats. Now you shall keep it until the fourteenth day of the same month. Then the whole assembly of the congregation of Israel shall kill it at twilight. And they shall take some of the blood and put it on the two doorposts and on the lintel of the houses where they eat it. Then they shall eat the flesh on that night; roasted in fire, with unleavened bread and with bitter herbs they shall eat it.