How Would Persecuted Christians Have Understood Psalms Promising Protection and Rescue?

Questions about how persecuted Christians would have understood Psalms promising protection and rescue, whether it’s a contradiction for Jesus to say that some will be put to death but also that not a hair of your head will perish, and whether the Bible has been added to throughout the years.

• How would Christians under persecution (such as those in Rome) have understood verses like Psalm 34:19–20 that promise protection and rescue by God for righteous people?
• Is it a contradiction for Jesus to say both that some will be put to death and that not a hair of your head will perish (Luke 21:16–19)?
• Is there evidence that would contradict my coworker’s claim that the Bible has been added to throughout the years?