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 great Day of wrath and terror,
That last Day of woe and doom,
Like a thief that comes at midnight,
On the sons of men shall come;
When the pride and pomp of ages
All shall utterly have pass'd,
And they stand in anguish, owning
That the end is here at last;
And the trumpet's pealing clangour,
Through the earth's four quarters spread,
Waxing loud and ever louder,
Shall convoke the quick and dead:
And the King of heavenly glory
Shall assume His throne on high,
And the cohorts of His angels
Shall be near Him in the sky:
And the sun shall turn to sackcloth,
And the moon be red as blood,
And the stars shall fall from heaven,
Whelm'd beneath destruction's flood.
Flame and fire, and desolation
At the Judge's feet shall go:
Earth and sea, and all abysses
Shall His mighty sentence know.
Then the elect upon the right hand
Of the Lord shall stand around;
But, like goats, the evil doers
Shall upon the left be found:
"Come, ye Blessed, take the kingdom,"
Shall be there the King's award,
"Which for you, before the world was,
Of My Father was prepared:
I was naked, and ye clothed Me;
Poor, and ye relieved Me; hence
Take the riches of My glory
For your endless recompense,"
Then the righteous shall make question,—
"When have we beheld Thee poor,
Lord of glory? When relieved Thee
Lying needy at our door?"
Whom the Blessed King shall answer,—
"When ye showed your charity,
Giving bread and home, and raiment,
What ye did was done to Me."
In like manner to the left hand
That most righteous Judge shall say,
"Go, ye cursed, to Gehenna,
And the fire that is for aye:
For in prison ye came not nigh Me,—
Poor, ye pitied not My lot;
Naked, ye have never clothed Me;
Sick, ye visited Me not."—
They shall say: "O Christ, when saw we
That Thou calledst for our aid,
And in prison, or sick, or hungry,
To relieve have we delayed?"
Whom again the Judge shall answer:
"Since ye never cast your eyes
On the sick, and poor, and needy,
It was Me ye did despise."
Backward, backward, at the sentence,
To Gehenna they shall fly,
Where the flame is never-ending,
Where the worm can never die;
Where are Satan and his angels
In profoundest dungeon bound;
Where are chains and lamentation,
Where are quenchless flames around.
But the righteous, upward soaring,
To the heavenly Land shall go,
Midst the cohorts of the angels,
Where is joy for evermo:
To Jerusalem, exulting,
They with shouts shall enter in;
That true "sight of peace" and glory
That sets free from grief and sin.
Christ shall they behold for ever,
Seated at the Father's hand,
As in Beatific Vision
His elect before Him stand.
Wherefore, man, while yet thou mayest,
From the dragon's malice fly;
Give thy bread to feed the hungry,
If thou seek'st to win the sky;
Let thy loins be straitly girded,
Life be pure, and heart be right;
At the coming of the Bridegroom,
That thy lamp may glitter bright.