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.
Storm and terror, grief and error,
Comes the Sun to chase away:
And the morning fast adorning
All the sky proclaims the day.
O true splendour, bright and tender,
Sun of Righteousness on high,
Port Thou showest, source Thou owest
To the Virgin's purity!
Now Thou keepest rest and sleepest
In that zodiac of delight;
Joy hereafter shall with laughter
Hail the coming Monarch's sight.
Satan, gnashing, sees it flashing
Through that cloud so pure and white:
Thou endurest ever purest,
Virgin Mother of the Light.
Darkness scattered, hell gates shattered,
Victory to the souls draws nigh,
Whom confession of transgression
Justly had condemned to die.
Earth rejoices: heavenly voices
Bender praise to God above;
Now renewing and hedewing
Every soul with fuller love. Amen.