As the reason for his departure, our Lord mentioned his desire to open the way for our ascent to the heavenly places and to prepare a safe passage for us by making smooth the road that had previously been impassable.
For heaven was then completely inaccessible to us – human foot had never trodden that pure and holy country of the angels.
It was Christ who first prepared the way for our ascent there.
By offering himself to God the Father as the firstfruits of all who are dead and buried, he gave us a way of entry into heaven and was himself the first man the inhabitants of heaven ever saw.
The angels in heaven, knowing nothing of the sacred and profound mystery of the incarnation, were astonished at his coming and almost thrown into confusion by an event so strange and unheard of.
[...] But the Spirit did not leave the heavenly throng ignorant of the wonderful wisdom of God the Father.
Commanding them to open the gates of heaven in honour of the king and master of the universe, he cried out: Lift up your gates, you princes, and be lifted up, you everlasting doors, that the king of glory may come in.
And so our Lord Jesus Christ has opened up for us a new and living way, as Paul says, not by entering a sanctuary made with hands, but by entering heaven itself to appear before God on our behalf.
For Christ has not ascended in order to make his own appearance before God the Father.
He was, is, and ever will be in the Father and in the sight of him from whom he receives his being, for he is his Father’s unfailing joy.
But now the Word, who had never before been clothed in human nature, has ascended as a man to show himself in a strange and unfamiliar fashion.
And he has done this on our account and in our name, so that being like us, though with his power as the Son, and hearing the command, Sit at my right hand, as a member of our race, he might transmit to all of us the glory of being children of God.
As man then he appeared before the Father on our behalf, to enable us whom original sin had excluded from his presence to see the Father’s face once more.
As the Son he took his seat to enable us as sons through him to be called children of God.
So Paul, who claims to speak for Christ, teaching that the whole human race has a share in the events of Christ’s life, says that God has raised us up with him and enthroned us with him in heaven.
Cyril of Alexandria (c. 376-444): Commentary on St John’s Gospel, 9 (PG 74:182-183); from the Monastic Office of Vigils, Sunday of the 7th Week of Eastertide, Year 2.