“Will You at this time,” say they, “restore the kingdom to Israel?” (Recapitulation). They so well knew his mildness, that after His Passion also they ask Him, “Will you restore?” And yet He had before said to them, “You shall hear of wars and rumors of wars, but the end is not yet,” nor shall Jerusalem be taken. But now they ask Him about the kingdom, not about the end. And besides, He does not speak at great length with them after the Resurrection. They address then this question, as thinking that they themselves would be in high honor, if this should come to pass. But He (for as touching this restoration, that it was not to be, He did not openly declare; for what needed they to learn this? Hence they do not again ask, “What is the sign of Your coming, and of the end of the world?” for they are afraid to say that: but, “Will You restore the kingdom to Israel?” for they thought there was such a kingdom), but He, I say, both in parables had shown that the time was not near, and here where they asked, and He answered thereto, “You shall receive power,” says He, “when the Holy Ghost has come upon you. Is come upon you,” not, “is sent,” [to show the Spirit's coequal Majesty. How then do you dare, O opponent of the Spirit, to call Him a creature?]. “And you shall be witnesses to Me.” He hinted at the Ascension. [And when he had spoken these things.] Which they had heard before, and He now reminds them of. [“He was taken up.”] Already it has been shown, that He went up into heaven. [“And a cloud, etc.”] “Clouds and darkness are under His feet,” says the Scripture: for this is declared by the expression, “And a cloud received Him:” the Lord of heaven, it means. For as a king is shown by the royal chariot, so was the royal chariot sent for Him. [Behold, two men, etc.] That they may vent no sorrowful exclamations, and that it might not be with them as it was with Elisha, who, when his master was taken up, rent his mantle. And what say they? “This Jesus, which is taken up from you into heaven, shall thus come.” And, “Behold, two men stood by them.” With good reason: for “in the mouth of two witnesses shall every word be established”: and these utter the same things. And it is said, that they were “in white apparel.” In the same manner as they had already seen an Angel at the sepulchre, who had even told them their own thoughts; so here also an Angel is the preacher of His Ascension; although indeed the Prophets had frequently foretold it, as well as the Resurrection.
Everywhere it is Angels as at the Nativity, “for that which is conceived in her,” says one, “is by the Holy Ghost”: and again to Mary, “Fear not, Mary.” And at the Resurrection: “He is not here; He is risen, and goes before you.” “Come, and see!” And at the Second Coming. For that they may not be utterly in amaze, therefore it is added, “Shall thus come.” They recover their breath a little; if indeed He shall come again, if also thus come, and not be unapproachable! And that expression also, that it is “from them” He is taken up, is not idly added. And of the Resurrection indeed Christ Himself bears witness (because of all things this is, next to the Nativity, nay even above the Nativity, the most wonderful: His raising Himself to life again): for, “Destroy,” He says, “this Temple, and in three days I will raise it up.” “Shall thus come,” say they. If any therefore desires to see Christ; if any grieves that he has not seen Him: having this heard, let him show forth an admirable life, and certainly he shall see Him, and shall not be disappointed. For Christ will come with greater glory, though “thus,” in this manner, with a body; and much more wondrous will it be to see Him descending from heaven. But for what He will come, they do not add.
Source: Homilies on Acts (New Advent)