Did you hear of the time when the Israelites had to put lamb’s blood on their doors? That was back when they were slaves in Egypt, and God was about to send the final plague to punish Pharaoh and convince him to let Israel be free. This is the plague that would kill the oldest son of every family, except for families that sacrificed a lamb and put the blood on their front door. The Israelites obeyed and they kept their sons safe; Egyptian families did not do it and so they lost their sons.
Pharaoh finally decided that making the Israelites stay would destroy Egypt because of the plagues God sent, so he let them go. He changed his mind pretty quickly though; soon after Israel started on their trip to the Promised Land, Pharaoh gathered his army and chased them down at the Red Sea. That's when God parted the sea through Moses, and the Israelites passed through safely. When Pharaoh tried to follow, God caused the Red Sea to crash on him and his men, and so God saved Israel.
Thinking back to the sacrifice of the lamb before the plague, it's actually something that points to the sacrifice of Jesus on the cross. The lamb saved Israel from slavery to Egypt, and Jesus saves everyone who believes in Him from slavery to sin. Pretty cool how so many things in the Bible tell us more about Jesus! Read more about the last plague in Exodus chapters 11 and 12.