Acts 1, 1-11.
I have spoken the first, dear Theophile, of all that Jesus began both to do and to teach, until the day that he was taken up, after he had commanded the apostles (whom he had named) by the Holy Spirit, whom he had manifested alive after his passion by many things; and he was seen among them forty days, and talked with them of the kingdom of God. And when he had gathered them together, he commanded them that they should not depart from Jerusalem, but wait for the promise of the Father, which ye have heard (said he) of me. For John baptized with water: but ye shall be baptized with the Holy Ghost not many days hence. And they that were come together asked him, saying: Lord, wilt thou at this time restore the kingdom to Israel? And he said unto them: It behooveth you not to know the time or the hour which the Father hath reserved for his power: but ye shall receive power from the Holy Ghost, which shall come upon you: and ye shall be my witnesses in Jerusalem, and in all Judea and Samaria, and unto the end of the earth. And when he had spoken these things, he was lifted up to be seen, and a cloud took him up from before their eyes. And as they looked after him toward heaven, behold, there stood by them two men clothed in white, which said also, Ye men of Galilee, why stand ye looking toward heaven? This Jesus, who is taken up from you into heaven, will come as you have seen him going into heaven.
This epistle is nothing other than the history or story of how Christ visibly ascended into heaven, and is in itself clear and easy to understand. But what is to be said of the article of Christ's ascension, we will save for the other sermons on the feasts of Christ throughout the year, since each article is also to be spoken of Christ in particular.