With these words Peter is simply drawing out that testing by fire (to see what you are made of) is normal in the experience of the Christian (see Matthew 10:17–25; John 15:18–25; Deuteronomy 8:2–5). Instead of responding with “surprise,” the Christian should expect and even welcome the testing (so as to be encouraged by its outcome).
12 Beloved, do not be surprised at the fiery trial when it comes upon you to test you, as though something strange were happening to you.