7 I know not how I should speak, for the wonder surpasses all description! The force of the fire was both quenched and not quenched: for while it came in contact with the bodies of these saints, it was quenched; but when it was needful to burst their bonds, it was not quenched; wherefore it broke their bonds, but touched not their ancles. Do you see how very near it was? Yet the fire was not deceived, and dared not penetrate within the bonds. The tyrant bound, and the flame set loose; that you might learn at once the fierceness of the barbarian, and the submissiveness of the element.
For what reason did he bind, when he was about to cast into the fire? In order that the miracle might be the greater; that the sign might be the more unaccountable; that you may not suppose that the things seen were an optical delusion. For if that fire had been no fire, it would not have consumed the bands; and what is much more, it would not have seized upon the soldiers who were placed without the furnace; but as the case was, it showed its power upon those without; but towards those within, its submissiveness.
But observe, I pray, in everything, how the devil by the very same means with which he fights with the servants of God, pulls down his own power; not intentionally, but because the wisdom and abundant contrivance of God turns all his weapons and devices upon his own head; which assuredly happened on that occasion. For the devil at that time inspiring the tyrant, neither suffered the heads of the saints to be cut off with the sword, nor that they should be delivered to wild beasts, nor punished in any such manner; but that they should be thrown into the fire; to the end that not even any relics of these saints should remain, their bodies being altogether consumed, and their ashes being mingled with the ashes of the fagots.
But God accordingly employed this very circumstance for the taking away of impiety. And how? I will tell you. Fire is accounted by the Persians to be a god; and the barbarians, who inhabit that country even now honour it with much worship. God, therefore, being desirous to pull up by the roots the material of impiety, permitted the punishment to take this form, in order that He might give the victory to His servants before the eyes of all these fire-worshippers; persuading them by the plain fact, that the gods of the Gentiles are in dread not of God only, but even of the servants of God.
Source: Homilies on the Statues (New Advent)