The word Peter uses means the process of burning and hence being burned. The thought is not new to Peter’s letter; see 1 Peter 1:7, where burning is clearly a purifying agent (as opposed to destroying). That this is the concept Peter intends is clear from what he writes later in this verse. The phrase fiery trial,
then, does not describe so much the intensity of what Peter’s readers (hinted at in 1 Peter 2:12, 1 Peter 2:19–20) were experiencing as its purpose.
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.