Why were the Israelites safe from the death of the firstborn — was it because they were good?
No. They were safe from the death of the firstborn solely because the blood was applied to their door in faith, not because they had earned it or were good. Scripture gives no indication any Jews were lost; every Jewish household in Goshen had the blood on the door and was secure.
Les explains that the Israelites were not spared because of their own goodness or anything they had earned. They had nothing to worry about and nothing to fear because the blood was on the door. That blood was applied as an act of faith. If they had refused to put the blood on the door and scoffed at it, they would not have been safe; they too would have lost their firstborn. The Scripture gives no indication that any Jews were lost; evidently every Jewish household in Goshen had the blood on the door and was safe. Les applies this to believers: those under the blood are safe and secure, though this never gives license. They did not have to weep and wail with “what ifs,” even though they were sinners just like we are. Les also says this exodus from Egypt was God’s redemption of the nation, and he plans to go into Romans and Ephesians to show this further.