Mencius - Book 1, Part 1, Chapter 7D

The king was pleased, and said, 'It is said in the Book of Poetry, "The minds of others, I am able by reflection to measure;" this is verified, my Master, in your discovery of my motive. I indeed did the thing, but when I turned my thoughts inward, and examined into it, I could not discover my own mind. When you, Master, spoke those words, the movements of compassion began to work in my mind. How is it that this heart has in it what is equal to the royal sway?'

Mencius replied, 'Suppose a man were to make this statement to your Majesty: "My strength is sufficient to lift three thousand catties, but it is not sufficient to lift one feather; my eyesight is sharp enough to examine the point of an autumn hair, but I do not see a wagon-load of faggots; "would your Majesty allow what he said?'

'No,' was the answer, on which Mencius proceeded, 'Now here is kindness sufficient to reach to animals, and no benefits are extended from it to the people. How is this? Is an exception to be made here? The truth is, the feather is not lifted, because strength is not used; the wagon-load of firewood is not seen, because the eyesight is not used; and the people are not loved and protected, because kindness is not employed. Therefore your Majesty's not exercising the royal sway, is because you do not do it, not because you are not able to do it.'
~ James Legge translation via nothingistic.org ~

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