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.
That substantive Word, united
To the flesh, and therein plighted
To a life of misery sore;
Him to be the co-eternal,
John's theology supernal
Testifieth evermore.
On his Master's bosom lying
Quaffed he thence that fount undying,
Wisdom's stream, his thirst to sate:
Then became, with touch endearing,
Faith to word, to teaching hearing,
Mind to God, conterminate.
Whence in ecstasy uprising,
Things of carnal sense despising,
And the clouds of error's night:
On the True Sun's truest vision
Soaring high, with full fruition,
Fix'd he fast his eagle sight.
Sense is naught, if style it slighteth:
He with style so subtle writeth,
And with sense so Catholic,
That the Word's true Incarnation
Never more can meet negation
From the wile of heretic.
Which with Virtue generative
All things made at earth's foundation:
That same Word, from John we gather,
Is not severed from the Father
Save by personal relation.
Him, Whom Matthew, more than other,
Sets forth, fed by spotless Mother,
Born for pain and woe discloses:
Whom Luke's pen, true ox-horn, showeth
On the Cross whence healing floweth,
As the serpent raised by Moses:
Him, to Whom from death's dejection
Lion-Mark brings Resurrection,
Rocks then riving, earth then quaking:
God of God, of Splendour, Splendour:
These the titles John could render,
Alpha and Omega making.
They relate the earthly passion,
How He died in mortal fashion,
Crowned with thorns, their suff'ring Lord:
He, upraised to things supernal,
Shows the King of realms eternal,
And the vengeance of His sword.
On these wings evangelistic
Rolls the Monarch's chariot mystic,
One among the Living Four:
While the harpers pour their praises,
And the adoring people raises
Alleluia evermore.