The following readings are taken from the office of Matins for the Feast of the Ascension, in the Tridentine Breviary as promulgated by Pope Pius V.
Lesson from the Acts of Apostles
1 The former treatise I made, O Theophilus, of all things which Jesus began to do and to teach,
2 Until the day on which, giving commandments by the Holy Ghost to the apostles whom he had chosen, he was taken up.
3 To whom also he showed himself alive after his passion, by many proofs, for forty days appearing to them, and speaking of the kingdom of God.
4 And eating together with them, he commanded them, that they should not depart from Jerusalem, but should wait for the promise of the Father, which you have heard (saith he) by my mouth.
5 For John indeed baptized with water, but you shall be baptized with the Holy Ghost, not many days hence.
6 They therefore who were come together, asked him, saying: Lord, wilt thou at this time restore again the kingdom to Israel?
7 But he said to them: It is not for you to know the times or moments, which the Father hath put in his own power:
8 But you shall receive the power of the Holy Ghost coming upon you, and you shall be witnesses unto me in Jerusalem, and in all Judea, and Samaria, and even to the uttermost part of the earth.
9 And when he had said these things, while they looked on, he was raised up: and a cloud received him out of their sight.
10 And while they were beholding him going up to heaven, behold two men stood by them in white garments.
11 Who also said: Ye men of Galilee, why stand you looking up to heaven? This Jesus who is taken up from you into heaven, shall so come, as you have seen him going into heaven.
12 Then they returned to Jerusalem from the mount that is called Olivet, which is nigh Jerusalem, within a sabbath day's journey.
13 And when they were come in, they went up into an upper room, where abode Peter and John, James and Andrew, Philip and Thomas, Bartholomew and Matthew, James of Alpheus, and Simon Zelotes, and Jude the brother of James.
14 All these were persevering with one mind in prayer with the women, and Mary the mother of Jesus, and with his brethren.
From the Sermons of Pope St. Leo the Great.
1st on the Lord's Ascension.
After the blessed and glorious Resurrection of our Lord Jesus Christ, wherein the Divine Power raised up in three days the true Temple of God Which the iniquity of the Jews had destroyed John ii. 19, God was pleased to ordain, by His Most Sacred Will, and in His Providence for our instruction and the profit of our souls, a season of forty days which season, dearly beloved brethren, doth end on this day. During that season the bodily Presence of the Lord still lingered on earth, that the reality of the fact of His having risen again from the dead might be armed with all needful proofs. The death of Christ had troubled the hearts of many of His disciples their thoughts were sad when they remembered His agony upon the Cross, His giving up of the Ghost, and the laying in the grave of His lifeless Body, and a sort of hesitation had begun to weigh on them.
Hence the most blessed Apostles and all the disciples, who had been fearful at the finishing on the Cross, and doubtful of the trustworthiness of the rising again, were so strengthened by the clear demonstration of the fact, that, when they saw the Lord going up into the height of heaven, they sorrowed not, nay they were even filled with great joy And, in all verity, it was a great an unspeakable cause for joy to see the Manhood, in the presence of that the multitude of believers, exalted above all creatures even heavenly, rising above the ranks of the angelic armies and speeding Its glorious way where the most noble of the Archangels lie far behind, to rest no lower than that place where high above all principality and power, It taketh Its seat at the right hand of the Eternal Father, Sharer of His throne, and Partaker of His glory, and still of the very man's nature which the Son hath taken upon Him.
Therefore, dearly beloved brethren, let us also rejoice with worthy joy, for the Ascension of Christ is exaltation for us, and whither the glory of the Head of the Church is passed in, thither is the hope of the body of the Church called on to follow. Let us rejoice with exceeding great joy, and give God glad thanks. This day is not only the possession of Paradise made sure unto us, but in the Person of our Head we are actually begun to enter into the heavenly mansions above. Through the unspeakable goodness of Christ we have gained more than ever we lost by the envy of the devil. We, whom our venomous enemy thrust from our first happy home, we, being made of one body with the Son of God, have by Him been given a place at the right hand of the Father with Whom He liveth and reigneth, in the unity of the Holy Ghost, one God, world without end. Amen.
From the Holy Gospel according to Mark
At that time Jesus appeared unto the eleven disciples as they sat at meat, and upbraided them with their unbelief and hardness of heart because they believed not them which had seen Him after He was risen. And so on.
Homily by Pope St Gregory the Great
29th on the Gospels
I may be allowed to say that the disciples' slowness to believe that the Lord had indeed risen from the dead, was not so much their weakness as our strength. In consequence of their doubts, the fact of the Resurrection was demonstrated by many infallible proofs. These proofs we read and acknowledge. What then assureth our faith, if not their doubt? For my part, I put my trust in Thomas, who doubted long, much more than in Mary Magdalene, who believed at once. Through his doubting, he came actually to handle the holes of the Wounds, and thereby closed up any wound of doubt in our hearts.
Now confirm to our minds the trustworthiness of the fact that our Lord did indeed rise again from the dead, it is well for us to remark one of the statements of Luke (Acts i. 4.) "Eating together with them, He commanded them that they should not (1 John xiv. 16, 17 xvi. 7.) depart from Jerusalem and a little afterward: "While they beheld, He was taken up, and a cloud received Him out of their sight." Consider these words, note well these mysteries. After "eating together with them He was taken up." He ate and ascended: that the fact of His eating might show the reality of the Body in Which He went up. But Mark telleth us that before the Lord ascended into heaven He upbraided His disciples; with their unbelief and hardness of heart. From this I know not why we should gather, but that the Lord then upbraided His disciples, for whom He was about to be parted in the body, to the end that the words which He spoke unto them as He left them might be the deeper imprinted on their hearts.
When then, He had rebuked the hardness of their heart, who command did He give them Let us hear. "Go ye into all the world and preach the Gospel to every creature." Was the Holy Gospel, then my brethren, to be preached to thing insensate, or to brute beasts, that the Lord said to His disciples "Preach the Gospel to every creature." Nay but by the words "every creature" we must understand man, in whom are combined qualities of all creatures. Being he hath in common with stones, life in common with trees, feeling in common with beasts, understanding in common with angels. If, then, man hath something in common with every creature, man is to a certain extent every creature. The Gospel, then, if it be preached to man only, is preached to every creature.