Theophylact of Bulgaria
The apostle added this to what had been said before. He noticed that some were scandalized by the afflictions that befell them, since peace is promised in the law to those who work for the Lord (Rom 2:10).
Although above, when he gave rules to servants, he briefly consoled them in a similar way, here he gives the matter fuller speech and says: beloved.
By this very name he immediately shows that afflictions happen to them not because God hates them, but because He loves them greatly.
"Do not be estranged" means the same as "do not be astonished" (xenizesthe). Then he called the afflictions a fiery trial, or burning, and thereby showed that they are sent upon them for testing.
Testing makes the thing tested very precious, as happens with gold and silver.