6. Then flew one of the seraphim to me. The Prophet shows what kind of relief was brought to him, when he was so terrified as to think that he was a dead man; and this confirms what we have already said, that purity of lips comes from God alone; for men can produce nothing of themselves but what is filthy and abominable. If it be objected that it is absurd to say that the Lord now cleansed him, as if his tongue had formerly been impure and profane, though it had been the instrument employed by the Holy Spirit, I have already replied sufficiently to that objection. The Lord had already cleansed him, but according to his degree. The cleansing which is now added is greater; for it has its enlargements and additions, which no man can obtain all at once.
We must not conclude, therefore, that Isaiah’s lips were impure, because they are now cleansed; but we ought to inquire why it is done. It was because the Lord intended to enlarge and extend his favor towards him, and to raise him to higher dignity, that he might have greater influence over the people; and this was rendered necessary by the character of the times, and the change which had taken place in the state.
The fire was taken from the altar, to intimate that it was divine or heavenly; for the law forbade any strange fire to be brought to it, (Leviticus 10:1,) because in sacred things every human mixture is absolute profanation. By this figure, therefore, Isaiah was taught that all purity flows from God alone.