Hebrews 8:13
7 “In calling it new” (he says), “He has made the first old: but that which decays and waxes old is ready to vanish away.” See what was hidden, how he has laid open the very mind of the prophet! He honored the law, and was not willing to call it “old” in express terms: but nevertheless, this he did call it. For if the former had been new, he would not have called this which came afterwards “new” also. So that by granting something more and different, he declares that “it was waxen old.” Therefore it is done away and is perishing, and no longer exists.
Having taken boldness from the prophet, he attacks it more suitably, showing that our [dispensation] is now flourishing. That is, he showed that [the other] was old: then taking up the word “old,” and adding of himself another [circumstance], the [characteristic] of old age, he took up what was omitted by the others, and says “ready to vanish away.”
The New then has not simply caused the old to cease, but because it had become aged, as it was not [any longer] useful. On this account he said, “for the weakness and unprofitableness thereof”, and, “the law made nothing perfect”; and that “if the first had been faultless, then should no place have been sought for the second.” And “faultless”; that is, useful; not as though it [the old Covenant] was obnoxious to any charges, but as not being sufficient. He used a familiar form of speech. As if one should say, the house is not faultless, that is, it has some defect, it is decayed: the garment is not faultless, that is, it is coming to pieces. He does not therefore here speak of it as evil, but only as having some fault and deficiency.
8. So then we also are new, or rather we were made new, but now have become old; therefore we are “near to vanishing away,” and to destruction. Let us scrape off this old age. It is indeed no longer possible to do it by Washing, but by repentance it is possible here [in this life]. If there be in us anything old, let us cast it off; if any “wrinkle,” if any stain, if any “spot,” let us wash it away and become fair: that “the King may desire our beauty.”
It is possible even for him who has fallen into the extremest deformity to recover that beauty of which David says that the King shall desire your beauty. “Hearken, O daughter, and consider; forget also your own people and your father's house: so shall the King greatly desire your beauty.” And yet forgetting does not produce beauty. Yea, beauty is of the soul. What sort of forgetting? That of sins. For he is speaking about the Church from among the Gentiles, exhorting her not to remember the things of her fathers, that is [of] those that sacrificed to idols; for from such was it gathered.
And he said not, “Go not after them,” but what is more, Do not admit them into your mind; which he says also in another place, “I will not mention their names through my lips.” And again, “That my mouth may not talk of the deeds of men.” As yet is this no great virtue; nay, rather, it is indeed great, but not such as this [which is here spoken of]. For what does he say there? He says not; “Talk not of the things of men, neither speak of the things of your fathers”; but, neither remember them, nor admit them into your mind. You see to how great a distance he would have us keep away from wickedness. For he that remembers not [a matter] will not think of it, and he that does not think, will not speak of it: and he that does not speak of it, will not do it. Do you see from how many paths he has walled us off? By what great intervals he has removed us, even to a very great [distance]?
9. Let us then also “hearken and forget” our own evils. I do not say our sins, for (He says) “Remember first, and I will not remember.” I mean for instance, Let us no longer remember rapacity, but even restore the former [plunder]. This is to forget wickedness, and to cast out the thought of rapacity, and never at any time to admit it, but to wipe away also the things already done amiss.
Whence may the forgetfulness of wickedness come to us? From the remembrance of good things, from the remembrance of God. If we continually remember God, we cannot remember those things also. For (he says) “When I remembered You upon my bed, I thought upon You in the morning dawn.” We ought then to have God always in remembrance, but then especially, when thought is undisturbed, when by means of that remembrance [a man] is able to condemn himself, when he can retain [things] in memory. For in the daytime indeed, if we do remember, other cares and troubles entering in, drive the thought out again: but in the night it is possible to remember continually, when the soul is calm and at rest; when it is in the haven, and under a serene sky. “The things which you say in your hearts be ye grieved for on your beds,” he says. For it were indeed right to retain this remembrance through the day also. But inasmuch as you are always full of cares, and distracted amidst the things of this life, at least then remember God on your bed; at the morning dawn meditate upon Him.
If at the morning dawn we meditate on these things, we shall go forth to our business with much security. If we have first made God propitious by prayer and supplication, going forth thus we shall have no enemy. Or if you should, you will laugh him to scorn, having God propitious. There is war in the market place; the affairs of every day are a fight, they are a tempest and a storm. We therefore need arms: and prayer is a great weapon. We need favorable winds; we need to learn everything, so as to go through the length of the day without shipwrecks and without wounds. For every single day the rocks are many, and oftentimes the boat strikes and is sunk. Therefore have we especially need of prayer early and by night.
Source: Homilies on the Epistle to the Hebrews (New Advent)