Jesus said to the disciples,
"...you will receive power when the Holy Spirit has come upon you,
and you will be my witnesses
in Jerusalem and in all Judea and Samaria,
and to the end of the earth.”

And when he had said these things,
as they were looking on, he was lifted up,
and a cloud took him out of their sight.
And while they were gazing into heaven as he went,
behold, two men stood by them in white robes,
and said,
“Men of Galilee, why do you stand looking into heaven?
This Jesus, who was taken up from you into heaven,
will come in the same way
as you saw him go into heaven.”

Acts 1:8-11

By your Gift, the Holy Ghost, we are set aflame and borne aloft,
and the fire within us carries us upward.
'Our hearts are set on an upward journey,' as we sing the 'song of ascents'.
It is your fire, your good fire, that sets us aflame and carries us upward.
For our journey leads us upward to the peace of the heavenly Jerusalem;
it was a 'welcome sound when I heard them saying,
We will go into the house of the Lord.'

St Augustine, Confessions, Bk XIII, para 9

"The Ascension of Christ proclaims and celebrates our spiritual destiny
as sons and daughters of God by adoption and grace...
“Our conversation is in heaven,” [Php 3:20]
and in the Church’s liturgy,
we find ourselves engaged in precisely that conversation,
“with angels and archangels and all the company of heaven”. 
Here, in liturgy, all the arts conspire to solicit mind and heart,
to wean the soul from worldliness. 
A door is opened into heaven."

Robert Crouse, A Sermon for Ascension

"...I am amazed that I should rise so high,
beyond the lightness of the air and fire."

She turned her eyes to me then with a sigh
of pity, as a mother in distress
whose child is ill and talks deliriously,
So she made matters plain:

"...No more amazement should it bring to you
that you ascend, than if a mountain stream
should tumble rushing to the plains below.
But it would be a cause of just surprise
if, free of every bar, you should remain
like a still flame on earth, and not arise."

Then to the heavens she turned her gaze again.

Dante and Beatrice ascending into the heavens,
Dante's Paradiso, Canto I, lines 98-103 and 136-142