Here is an excerpt from something I did a few years ago for my Patristic Rosary Project:
2nd Glorious Mystery: The Ascension
Everything about the life of the Lord is a blessing for us. After His resurrection the Lord blessed the Apostles with His presence, gloriously risen. When His earthly work with them was completed, He very explicitly blessed them. “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.” (Luke 24:50-51). Even the Lord’s departure from us was a blessing and it occurred in the midst of Christ’s explicit blessing of His apostles. Venerable Bede (+735) speaks of the Lord’s blessing:
Our Redeemer appeared in the flesh to take away sins, remove what humans deserved because of the first curse, and grant believers an inheritance of everlasting blessing. He rightly concluded all that He did in the world with words of blessing. He showed that He was the very one of whom it was said, “For indeed He who gave the law will give a blessing.” (Ps 83:8 Vulgate) It is appropriate that He led those who He blessed out to Bethany, which is interpreted “house of obedience”. Contempt and pride deserved a curse, but obedience deserved a blessing. The Lord Himself was made obedient to His Father even unto death, so that He might restore the lost grace of blessing to the world. He gives the blessing of heavenly life only to those who strive in the holy Church to comply with the divine commands. [Homilies on the Gospels 11.15]
Remember that for Bede, like most of the Fathers, the details have spiritual meanings. Even the place to which the Lord led the Apostles meant something:
We must not pass over the fact that Bethany is on the slope of the Mount of Olives. Just as Bethany represents a Church obedient to the commands of the Lord, so the Mount of Olives quite fittingly represents the very Person of our Lord. Appearing in the flesh, he excels all the saints, who are simply human beings, by the loftiness of His dignity and the grace of His spiritual power.
St. Cyril of Alexandria (+444) speaks of the blessing the Lord confers:
Having blessed them and gone ahead a little, he was carried up into heaven so that He might share the Father’s throne even with the flesh that was united to Him. The Word made this new pathway for us when He appeared in human form. After this, and in due time, He will come again in the glory of His Father with the angels and will take us up to be with Him. Let is glorify Him.
We may not at all times remember that even at this very instant our human nature is, in the divine Person of Our Lord, seated at the right hand of the Father. We are therefore in a state of “already but not yet”: humanity is enthroned in heaven sharing something of God’s glory, and yet we are still here, awaiting the final realization of all Christ accomplished. St. Leo the Great (+461) pries this open:
Dearly beloved, through all this time between the resurrection of the Lord and His ascension, the providence of God thought of this, taught this and penetrated their eyes and hearts. He wanted them to recognize the Lord Jesus Christ as truly risen, who was truly born, truly suffered and truly died. The manifest truth strengthened the blessed apostles and all the disciples who were frightened by His death on the Cross and were doubtful of His resurrection. The result was the were not only afflicted with sadness but also filled with “great joy” when the Lord went into the heights of heaven. It was certainly a great and indescribable source of joy when, in the sight of the heavenly multitudes, the nature of our human race ascended over the dignity of all heavenly creatures. It passed the angelic orders and was raised beyond the heights of archangels. In its ascension, our human race did not stop at any other height until this same nature was received at the seat of the eternal Father. Our human nature, united with the divinity of the Son, was on the throne of His glory. The ascension of Christ is not elevation. Hope for the body is also invited where the glory of the Head preceded us. Let us exalt, dearly beloved, with worthy joy and be glad with a holy thanksgiving. Today we not only are established as possessors of paradise, but we have even penetrated the heights of the heavens in Christ. The indescribable grace of Christ, which we lost through the ill will of the devil, prepared us more fully for that glory. Incorporated within Himself, the Son of God placed those whom the violent enemy threw down from the happiness of our first dwelling at the right hand of the Father. The Son of God lives and reigns with God the Father almighty and with the Holy Spirit forever and ever. Amen. [s. 73.3-4]
Before His ascension, the Lord laid a great commission on the apostles. Here is St. Jerome (+420):
“Jesus approached them and said, ‘All authority in heaven and earth has been given to me.'” This authority was given to one who had just been crucified, buried in a tomb, laid dead, and afterwards had arisen. Authority was given to Him in both heaven and earth so that He who once reigned in heaven might also reign on earth through the faith of His believers. “Go therefore and teach all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.'” First they teach all nations; then they baptize those they have taught with water for the body is not able to receive the sacrament of baptism before the soul has received the truth of the faith. They were baptized in the name of the Father and of the Son and of the Holy Spirit so that the three who are one in divinity might also be one in giving themselves. The name of the Trinity is the name of the one God. “‘Teach them to observe all that I have commanded you.'” What a marvelous sequence this is. He commanded the apostles first to teach all nations and then to baptize them in the sacrament of faith and then, after faith and baptism, to teach them to observe all that He had commanded. Lest we think these commandments of little consequence or few in number, he added, “all that I have commanded you,” so that those who were to believe and be baptized in the Trinity would observe everything they had been taught. [Commentary on Matthew 4.28.18-19]
This is a heavy charge, but the Lord consoles them as well. St. John Chrysostom (+407) makes this point:
After that, because he had enjoined on them great things, to raise their courage He reassures them that He will be with then always, “even to the end of the world.” Now do you see the relation of His glory to His previous condescension? His own proper power is again restored. What He had said previously was spoken during the time of His humiliation. He promised to be not only with these disciples but also with all who would subsequently believe after them. Jesus speaks to all believers as if to one body. Do not speak to me, He says, of the difficulties you will face, for “I am with you,” as the one who makes all things easy. Remember that this is also said repeatedly to the prophets in the Old Testament. Recall Jeremiah objecting that He is too young and Moses and Ezekiel shrinking from the prophet’s office. “I am with you” is spoken to all these people. [The Gospel of Matthew, Homily 90.2]