Albert Barnes on 1 Peter 4:12

Beloved, think it not strange. Do not consider it as anything which you had no reason to expect; as anything which may not happen to others also.

Concerning the fiery trial which is to try you. Referring, doubtless, to some severe persecution which was then impending. We have not the means of determining precisely what this was. The word rendered fiery trial (πυρωσει) occurs only here and in Rev 18:9,18; in both of which latter places it is rendered burning. It means, properly, a being on fire, burning, conflagration; and then any severe trial. It cannot be demonstrated from this word that they were literally to suffer by fire, but it is clear that some heavy calamity was before them.

As though some strange thing happened unto you. Something unusual; something which did not occur to others.

(c) "fiery trial" 1Cor 3:13