This text comes from Mediaeval Hymns and Sequences, edited by John Mason Neale, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
Gabriel, from the Heaven descending,
On the faithful Word attending,
Is in holy converse blending
With the Virgin full of grace:
That good word and sweet he plighteth
In the bosom where it lighteth,
And for Eva Ave writeth,
Changing Eva's name and race.
At the promise that he sendeth
God the Incarnate Word descendeth;
Yet no carnal touch offendeth
Her, the undefiled one.
She, without a father, beareth,
She no bridal union shareth,
And a painless birth declareth
That she bare the Royal Son.
Tale that wondering search entices!
But believe,—and that suffices;
It is not for man's devices
Here to pry with gaze unmeet:
High the sign, its place assuming
In the bush, the unconsuming:
Mortal, veil thine eyes presuming,
Loose thy shoes from off thy feet!
As the rod, by wondrous power,
Moistened not by dew or shower,
Bare the almond and the flower,
Thus He came, the Virgin's Fruit:
Hail the fruit, O world, with gladness!
Fruit of joy and not of sadness:
Adam had not lapsed to madness
Had he tasted of its shoot.
Jesus, kind above all other,
Gentle Child of gentle Mother,
In the stable born our Brother,
Whom the angelic hosts adore:
He, once cradled in a manger,
Heal our sin and calm our danger;
For our life, to this world stranger,
Is in peril evermore. Amen.