Isidore of Seville : After these plagues come blows from on high: voices, thunder and hail, and flashing fire. Thunder means reproaches and divine rebukes, because it does not strike in silence. It makes sounds and sends its teaching down from heaven. By its teaching the world is castigated and can acknowledge its guilt.And he sends hail, which destroys the young vices that are still tender. He sends fire, too, knowing that there are thorns and spiny plants which that fire might feed on. The Lord says of them, "I came to cast fire on the earth." This fire consumes the incentives to pleasure and lust. — QUESTIONS ON THE OLD TESTAMENT, Exodus 14:12-13