Before the Israelites left Egypt, God gave Moses instructions for a special meal that would take place on the night of their deliverance. Each family was to choose a lamb without blemish, kill it, and put its blood on the doorposts and lintel of their house. That night they were to eat the lamb with unleavened bread and bitter herbs and be ready to leave Egypt quickly.

God said that He would pass through Egypt that night and strike down the firstborn in every Egyptian household, but when He saw the blood on the doorposts, He would pass over that house and the people inside would be spared. That night there was great mourning throughout Egypt because many people died, including Pharaoh's firstborn son.

Pharaoh finally told Moses and the Israelites to leave Egypt. The Israelites left in such haste that their bread did not have time to rise, which is why they ate unleavened bread. God commanded them to celebrate the Passover every year to remember how He delivered them from slavery in Egypt.