Thomas Aquinas — on Isa 6:6 (Commentary on Isaiah)

“222. And one of the seraphim flew to me. Here he shows his purity from the cleansing of his sins. And concerning this he sets out three things. The minister of the cleansing: one of the seraphim flew to me. The instrument of cleansing: and in his hand was a live coal . . . off the altar of holocausts. The inner altar was made of earth as is said in Exodus 20:24: you shall make an altar of earth unto me; all around, however, was made of stone, where the fires of sacrifice were assembled; from these he took the coal. With the tongs, that is, with an instrument having two arms, by which receptive virtue may be signified, and by the altar, divine light itself or goodness, and by the coal, the gift received for the office of cleansing. Or by the fire tribulation may be signified; by the seraphim, Christ; by the tongs, the two testaments; by the coal, charity, which is in his hand, that is, his works. 223. But against this it is objected that Dionysius says, that those who belong to the higher orders are not sent in service; but it is certain that the seraphim are the highest; therefore it does not seem true that they came to cleanse the prophet. To which is to be said that Gregory touches on this question in a certain homily concerning the hundred sheep, and he leaves it in doubt. Dionysius, however, expressly holds that only the inferior orders are sent to us; and he says this is by the order of divine law that lower things are restored through the middle. But he explains what is said here in two ways. In one way, he says that this cleansing angel is called a seraph equivocally, not from his order, but from the act which he was then carrying out, because he cleansed with fire, and "seraph" means "fire"; in another way, he explains it saying that he is called a seraph properly because he is of this order, and he is said to cleanse, not because he himself immediately cleanses, but because by his authority, or by an illumination received from him, a lower angel cleansed; and he gives an example: it is just as a bishop is said to absolve when another absolves by his authority. And therefore because of reverence, the lower angel, who formed the vision, restores to God first, and to the seraph second, as if he were saying: "I cleanse you by light received from God, by the mediation of a seraph." In verse 6, instead of live coal, the Septuagint has carbuncle, because of their similarity to fire, for they have a flaming color.”