Tome of Divinity

The Tome of Divinity is a book of great value to the Clerics of Northshire Abbey. During the First War it somehow ended up in the clutches of Turok and his band of ogres. Anduin Lothar led an expedition into the Deadmines to recapture the tome, but the ogres emerged victorious in the dark depths of the mines. Anduin and a few survivors were captured and made prisoners to be killed slowly.

In a vision Anduin Lothar was seen alive, and he was rescued by soldiers from Stormwind. The Tome of Divinity was taken out of the mine with Lothar, though Turok was not stopped. Finally the tome was returned to Northshire Abbey.

It is currently used in the training of new paladins in both Stormwind City and Ironforge, and even the draenei keep copies to give out to their young vindicators as well.

Other lines
The trading card game reveals additional quotes from the book in some of its flavor texts:
 * "The enemy's dark resolve will seep away in the light of your righteousness." - about Judgement of Light
 * "The enemy's shadowy cunning is no match for the pure insight of the light." - about Judgement of Wisdom

Speculation
The tome might have been a libram.