John Cassian — on Sir 2:5 (CONFERENCES 1:7.25)

“We know that even the saints have been given over in the flesh to Satan and to great afflictions for some very slight faults, since the divine mercy will not suffer the very least spot or stain to be found in them on the day of judgment. He purges every spot of filth they have while in this world as the prophet, or rather God himself says, in order that he may commit them to eternity as gold or silver refined and needing no punishment for purification. "And," he says, "I will entirely purge your dross, and I will take away all your tin. And after this you will be called the city of the just, a faithful city." And again: "Just as silver and gold are tried in the furnace, so the Lord chooses the hearts." And again, "The fire tries gold and silver, but human beings are tried in the furnace of humiliation." And this also, "For whom the Lord loves he chastens, and scourges every child whom he receives."”