Then [Jesus] opened their minds to understand the Scriptures, and said to them, “Thus it is written, that the Christ should suffer and on the third day rise from the dead, and that repentance and forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem. You are witnesses of these things. And behold, I am sending the promise of my Father upon you. But stay in the city until you are clothed with power from on high.” Then he led them out as far as Bethany, and lifting up his hands he blessed them. While he blessed them, he parted from them and was carried up into heaven. And they worshiped him and returned to Jerusalem with great joy, and were continually in the temple blessing God. (Lk 24:45-51)

(Icon of the Ascension)

The Dismissal for Ascension Day from the Divine Liturgy of Our Father Among the Saints John Chrysostom (Byzantine Catholic):

May Christ our true God, Who, for our salvation, ascended from us to heaven and is seated at the right hand of God and Father, through the prayers of His most holy Mother; of the holy, glorious, and all‐praised Apostles; of our holy father, John Chrysostom; Archbishop of Constantinople; and of all the Saints, have mercy on us and save us, for He is good and loves mankind. 

The Early Church Father, Saint Leo, Bishop of Rome, is the theologian who has given us the Sermon (73) on the Ascension of Jesus Christ. Below is an excerpt from his sermon. If you are seeking to read the short sermon, click here and you will be directed to New Advent –

“Since then Christ’s Ascension is our uplifting, and the hope of the Body is raised, whither the glory of the Head has gone before, let us exult, dearly-beloved, with worthy joy and delight in the loyal paying of thanks. For today not only are we confirmed as possessors of paradise, but have also in Christ penetrated the heights of heaven, and have gained still greater things through Christ’s unspeakable grace than we had lost through the devil’s malice.”