One of the great Puritans Thomas Watson speaks to the zealousness of men:
How zealous men have been in a false religion! “They lavish gold out of the bag, and weigh silver in the balance” (Isaiah 46:6). The Jews did not spare any cost in their idolatrous worship. No, they “cause their sons and daughters to pass through the fire to Molech” (Jer. 32:35). They were so zealous in their idol worship that they would sacrifice their sons and daughters to their false gods. How far the blind heathen went in their false zeal! When the tribunes of Rome complained that they needed gold in their treasuries to offer to Apollo, the Roman matrons plucked off their chains of gold, and rings, and bracelets—and gave them to the priests to offer up sacrifice. Were these so zealous in their sinful worship, and will you not be zealous in the worship of the true God?
Do you lose anything by your zeal? Shall it not be superabundantly recompensed? What is heaven worth? What is a sight of God worth? Was not Jesus Christ zealous for you? He sweat drops of blood, he conflicted with his Father’s wrath. How zealous he was for your redemption, and have you no zeal for him? Is there anything you yourselves hate more than dullness and slothfulness in your servants? You are weary of such servants. Do you dislike a dull spirit in others, and not in yourselves? What are all your duties without zeal but mere fancies and nonentities?
Thomas Watson, The Godly Man’s Picture.
HT: Gairney Bridge