18. Septuagint: "And he had in his hand a coal, which he had taken from the altar with tongs, and he touched my mouth." Aquila and Theodotion: "And in his hand was a stone in tongs, which he had taken from the altar, and he touched my mouth." Symmachus: "And in his hand was a stone in tongs, which he had taken from the altar, and he brought it to my mouth." As for the history, it seems that God is sitting in the Temple of Jerusalem, and before him a coal is brought from the altar, according to the Septuagint to Isaiah: but from the altar of incense or burnt offerings. But as for mystical understanding, that fire is sent to us, which Jeremiah could not bear: so when it penetrates the secrets of our souls, it dissolves us, so that we are cooked from the old man into the new, that we may be able to break out into that voice: "And I live, now not I; but Christ lives in me." (Galatians 2:20) Tongs, too, although they were always in the priestly equipment, according to the other Interpreters, we owe various graces, by which God spoke in many ways and in many ways to our fathers in the prophets of old. Because in Hebrew the word for coal is read as "calculus," it seems to me that the divine speech is signified by the appellation of "stone". For just as a calculus is a type of stone, the hardest and roundest, and smoothest of all purity, so the word of God, which cannot yield to the contradictions of heretics or any adversaries, is called a calculus. Sephora circumcised her son with this stone, and Jesus purges the people of their sins, and in the Apocalypse the Lord promises to those who overcome that they shall receive a stone and on it a new name written. And it seems to me that the Septuagint, in translating it as ἄνθρακα, meant the same thing as the others. For ἄνθραξ, which we interpret as a carbuncle, is a type of shining and glittering stone, which we also find among the twelve stones. Therefore, whether we accept it as a calculus or a carbuncle stone, in the calculus of divine discourse there is truth and rigor, and in the shining carbuncle, doctrine is shown and revealed. "The words of the Lord are pure words, like silver tried in a furnace on the earth, purified seven times" (Ps. 12:6). And elsewhere: "The commandment of the Lord is clear, enlightening the eyes" (Ps. 19:8). As for what is said, "He had a coal in his hand," we should understand the work of his hands, as in "In the hand of the tongue is death and life" (Prov. 18:21); and in the Psalm: "They will fall by the sword in their hands" (Ps. 63:10). Or indeed, a hand appeared truly, so that the Prophet would not be afraid, by the likeness of a human form, when he sees the hand reaching out: in the same way we have seen God himself and the Angels change into human forms, so that fear would be removed from those who saw them.
19. Septuagint: And he said, behold your lips have touched this, and your iniquities shall be taken away, and your sins shall be cleansed. Aquila: Behold, these lips have touched you, and your iniquity shall depart, and your sin shall be propitiated. Other translators agree with Aquila's words. First, it is necessary for our lips to be touched; then, when they have been touched, iniquity is driven away; and when iniquity has been driven away, the Lord will be propitiated, because there is forgiveness with Him, and according to the Apostle: He himself is the propitiation for our sins. But with our sins having been cleansed, we will hear the voice of the Lord saying: Whom shall I send? And we will answer: Here I am, send me.
20. Septuagint: And I heard the voice of the Lord saying, Whom shall I send, and who will go to this people? Aquila, Theodotion, and Symmachus: And I heard the voice of the Lord saying, Whom shall I send? and who will go for us? We have discussed elsewhere the comparison between Isaiah and Moses, how one refused the ministry and the other offered himself voluntarily and endured hardships. But lest we seem to have omitted anything from those which the Jews call the "second books" and in which they place all knowledge, we will briefly touch upon why it is written in Hebrew, "who will go for us?" For just as it is said in Genesis, "Let us make man in our image and likeness" (Gen. 1:26), so here, I think, it is said, "who will go for us?" But for whom else should we consider ourselves, if not for the Father and the Son and the Holy Spirit, to whom everyone goes who follows their will? And in this, in that the voice of one speaker is proposed, there is a unity of divinity. But in that which is said 'to us,' a diversity of persons is indicated. We read in the Song of Songs the voice of the bridegroom saying to the bride: Arise, come, my love, my fair one, my dove: for winter is now past, the rain is over and gone. (Cant. 5.2). For when the soul feels tranquility in thought, when it is founded upon a rock, and its faith is fixed with deep roots, all the waves of temptation pass over it, and do not pass over him who is tempted. Note, however, how the Prophet responded in part to what the Lord had said, "Whom shall I send, and who will go for us?" Behold, I, send me," and was silent about the following, understanding that no man was worthy to go to God and make all his way his own, who sent him. The Lord, observing this humility, that he regarded himself as unworthy of the second place, commanded the following, saying: Go.
21. Septuagint: And he said, "Here I am, send me." Aquila and Theodotion: "Here I am, send me." Symmachus: Behold, send me. God, who calls those things that are not as though they were, and who said, "I am who I am"; and elsewhere, "He who is sent me" (Exodus 3.14), whoever he calls, he immediately causes to exist. This is sufficiently clear from the examples in the living Matthew the Evangelist and in Lazarus, who was dead for four days: as soon as they are called by the Lord, he left the tomb of greed, and the latter left his death (Mark 2, Luke 5, and John 11). For everything that is not with him is not. Wherefore, the Prophet, having been purged of faults, dared to say, "Behold, I am"; although in Latin codices, because of the variation of interpreters, "I am" is not added. Some think it should be noted to whom the speech of the sender or the sent is directed, which in Greek is called "Apostle." And they want this to be the difference: that whoever is sent is equally a Prophet and an Apostle; but those to whom the sender's speech is not given are only Prophets: which I think is superfluous. And because we once came to treat of this word, it should be known that Silas, a colleague of Paul, is called an Apostle in the Hebrew language, who writes some Epistles with him. And it is mistakenly read Silvanus for Silas, since we do not read Silvanus in the Acts of the Apostles.