Mencius - Book 3, Part 2, Chapter 5A

Wan Chang asked Mencius, saying, 'Sung is a small State. Its ruler is now setting about to practice the true royal government, and Ch'î and Ch'û hate and attack him. What in this case is to be done?'

Mencius replied, 'When T'ang dwelt in Po, he adjoined to the State of Ko, the chief of which was living in a dissolute state and neglecting his proper sacrifices. T'ang sent messengers to inquire why he did not sacrifice. He replied, "I have no means of supplying the necessary victims." On this, T'ang caused oxen and sheep to be sent to him, but he ate them, and still continued not to sacrifice. T'ang again sent messengers to ask him the same question as before, when he replied, "I have no means of obtaining the necessary millet."

On this, T'ang sent the mass of the people of Po to go and till the ground for him, while the old and feeble carried their food to them. The chief of Ko led his people to intercept those who were thus charged with wine, cooked rice, millet, and paddy, and took their stores from them, while they killed those who refused to give them up. There was a boy who had some millet and flesh for the laborers, who was thus slain and robbed. What is said in the Book of History, "The chief of Ko behaved as an enemy to the provision-carriers," has reference to this.

'Because of his murder of this boy, T'ang proceeded to punish him. All within the four seas said, "It is not because he desires the riches of the kingdom, but to avenge a common man and woman."
~ James Legge translation via nothingistic.org ~

Go here to read the introductory post to this serialized version of the Works of Mencius.