This text comes from Poems on Slavery, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
The pages of thy book I read,
And as I closed each one,
My heart, responding, ever said,
"Servant of God! well done!"
Well done! Thy words are great and bold;
At times they seem to me,
Like Luther's, in the days of old,
Half-battles for the free.
Go on, until this land revokes
The old and chartered Lie,
The feudal curse, whose whips and yokes
Insult humanity.
A voice is ever at thy side
Speaking in tones of might,
Like the prophetic voice, that cried
To John in Patmos, "Write!"
Write! and tell out this bloody tale;
Record this dire eclipse,
This Day of Wrath, this Endless Wail,
This dread Apocalypse!