Hebrews 10:26-27
“For if we sin willfully, after we have received the knowledge of the truth, there remains no more sacrifice for sins, but a certain fearful looking for of judgment, and fiery indignation which shall devour the adversaries.”
1. Trees which have been planted, and have had the advantage of all other care, and the hands and the labors of the cultivator, and yet yield no return for the labors, are pulled up by the roots, and handed over to the fire. So somewhat of this kind takes place also in the case of our Illumination. For when Christ has planted us, and we have enjoyed the watering of the Spirit, and then show no fruit; fire, even that of Hell, awaits us, and flame unquenchable.
Paul therefore having exhorted them to love and to bringing forth the fruit of good works, and having urged them from the kindlier [considerations] (What are these? That we have an entrance into the holy of holies, “the new way which He has inaugurated for us.”), does the same again from the more gloomy ones, speaking thus. For having said, “not forsaking the assembling of ourselves together, as the manner of some is, but exhorting one another, and so much the more, as you see the day approaching”, this being sufficient for consolation, he added, “For if we sin willfully after we have received the knowledge of the truth.” There is need, he means, of good works, yea, very great need, “For if we sin willfully after we have received the knowledge of the truth, there remains no more sacrifice for sins.” You were cleansed; you were set free from the charges against you, you have become a son. If then thou return to your former vomit, there awaits you on the other hand excommunication and fire and whatever such things there are. For there is no second sacrifice.
2. At this place we are again assailed by those who take away repentance, and by those who delay to come to baptism. The one saying, that it is not safe for them to come to baptism, since there is no second remission: And the other asserting that it is not safe to impart the mysteries to those who have sinned, if there is no second remission.
What shall we say then to them both? That he does not take away repentance, nor the propitiation through repentance, nor does he thrust away and cast down with despair the fallen. He is not thus an enemy of our salvation; but what? He takes away the second Washing. For he did not say, no more is there repentance, or no more is there remission, but “no more” is there a “sacrifice,” that is, there is no more a second Cross. For this is what he means by sacrifice. “For by one sacrifice,” he says, “He has perfected forever them that are sanctified”; not like the Jewish [rites.]. For this reason he has treated so much throughout concerning the Sacrifice, that it is one, even one; not wishing to show this only, that herein it differed from the Jewish [rites], but also to make [men] more steadfast, so that they might no longer expect another sacrifice according to the Jewish law.
“For,” says he, “if we sin willfully.” See how he is disposed to pardon. He says, “if we sin willfully,” so that there is pardon for those [who sin] not willfully. “After the knowledge of the truth”: He either means, of Christ, or of all doctrines. “There remains no more sacrifice for sins,” but what? “A certain fearful looking for of judgment and fiery indignation which shall devour the adversaries.” By “Adversaries” he means not the unbelievers, but those also who do what is against virtue; or [else he means] that the same fire shall receive them of the household also, which [receives] “the adversaries.” Then expressing its devouring nature, he says, as if giving it life, “fiery indignation which shall devour the adversaries.” For as a wild beast when irritated and very fierce and savage, would not rest till it could lay hold on some one and eat him up; so also that fire, like one goaded by indignation, whatever it can lay hold of does not let go, but devours and tears it to pieces.
3. Next he adds also the reason of the threat, that it is on good grounds, that it is just; for this contributes to confidence, when we show that it is just.
Source: Homilies on the Epistle to the Hebrews (New Advent)