Now that these things should have occurred at “the third hour,” was not without cause. For the brightness of this fire is shown at the very time when people are not engaged in their works, nor at dinner; when it is bright day, when all are in the market-place. Do you observe also the freedom which fills his speech? “And hearken to my words.” And he added nothing, but, “This,” says he, “is that which was spoken by the prophet Joel; And it shall come to pass in the last days.” He shows, in fact, that the consummation is near at hand, and the words, “In the last days,” have a kind of emphasis. [“I will pour out,” etc.] And then, that he may not seem to limit the privilege to the sons only, he subjoins, “And your old men shall dream dreams.”
Mark the sequence. First sons; just as David said, “Instead of your fathers, were begotten your sons.” And again Malachi; “They shall turn the hearts of the fathers to the children. And on my handmaidens, and on my servants.” This also is a token of excellence, for we have become His servants, by being freed from sin. And great is the gift, since the grace passes over to the other sex also, not as of old, it was limited to just one or two individuals, as Deborah and Huldah. He did not say that it was the Holy Ghost, neither did he expound the words of the prophet; but he merely brings in the prophecy to fight its own battle.
As yet also he has said nothing about Judas; and yet it was known to all what a doom and punishment he had undergone; for nothing was more forcible than to argue with them from prophecy: this was more forcible even than facts. For when Christ performed miracles, they often contradicted Him. But when Christ brought forward the prophet, saying, “The Lord said unto my Lord, Sit on my right hand,” they were silent, and “no man,” we read, “was able to answer Him a word.” And on all occasions He Himself also appealed to the Scriptures; for instance, “If he called them gods to whom the word of God came.” And in many places one may find this.
On this account here also Peter says, “I will pour out of my spirit upon all flesh;” that is, upon the Gentiles also. But he does not yet reveal this, nor give interpretations; indeed, it was better not to do so (as also this obscure saying, “I will show wonders in heaven above,” put them the more in fear because it was obscure.) And it would have been more an offense, had it been interpreted from the very first. Then besides, even as plain, he passes over it, wishing to make them regard it as such.
But after all, he does interpret to them anon, when he discourses to them upon the resurrection, and after he has paved the way by his discourse. (infra v. 39.) For since the good things were not sufficient to allure them, [it is added, “And I will show wonders, etc.”]. Yet this has never been fulfilled. For none escaped then [in that former judgment], but now the faithful did escape, in Vespasian's time. And this it is that the Lord speaks of, “Except those days had been shortened, not all flesh should be saved.”— [“Blood, and fire, and vapor of smoke.”] The worst to come first; namely, the inhabitants to be taken, and then the city to be razed and burnt.
Then he dwelt upon the metaphor, bringing before the eyes of the hearers the overthrow and the taking. “The sun shall be turned into darkness, and the moon into blood.” What means, the moon turned into blood? It denotes the excess of the slaughter. The language is fraught with helpless dismay. (supra p. 32.) “And it shall come to pass, every one who shall call upon the name of the Lord shall be saved. Every one,” he says: though he be priest (but he does not vet reveal the meaning), though bond, though free.
For there is no male nor female in Christ Jesus, no bond, no free. Well may it be so, for all these are but shadow. For if in king's palaces there is no high-born nor low-born, but each appears according to his deeds; and in art, each is shown by his works; much more in that school of wisdom (φιλοσοφια). “Every one who shall invoke.” Invoke: not any how, for it is written, “Not every one that says unto Me, Lord, Lord:” but with (διαθέσεως) inward earnest affection, with a life more than commonly good, with the confidence which is meet. Thus far, however, he makes the discourse light, by introducing that which relates to faith, and that terrible which relates to the punishment. For in the invocation is the salvation.
Source: Homilies on Acts (New Advent)