The first mention of Passover is in Exodus 12: 1-13, when the Lord tells Moses and his brother Aaron what they must do to avoid the tenth plague, and the meal they must eat before they leave Egypt. They are told that each family is to take a lamb, and the lamb is supposed to be a male, no more than a year old, and without any flaws. The lambs are taken care of for 14 days, and then are slaughtered at midnight. That same night they painted the doorframes red with the lamb’s blood, and roasted the entire lamb over a fire. The lamb was to be cooked with bitter herbs and served with unleavened bread. If a family was not big enough to eat an entire lamb, they were supposed to join another family, because the entire lamb had to be eaten that night.