What did the Jews in Egypt have to do to be protected from the death angel?
The Jews in Egypt were instructed to kill the sacrificial lamb and place its blood on the two doorposts and the lintel of their houses. Staying inside those homes, they were covered by the blood, and the death angel passed over them, so they had nothing to fear.
Les explains that these Jews had been slaves in Egypt and were told to kill the sacrificial lamb, put the blood on the two doorposts and the lintel, and sit in their little huts and houses. At midnight the death angel would go over Egypt and kill every firstborn male. As Israel huddled in their small abodes, those of faith were not in fear, because the blood was on the door and they were secure and covered. Les connects this to the church age: Paul brings it up, showing that Christ is our Passover; when Christ died on the Roman cross, His blood was shed, and when we come under that blood, we are passed over from any judgment.