Mencius - Book 4, Part 2, Chapter 24

P'ang Mang learned archery of Î. When he had acquired completely all the science of Î, he thought that in all the kingdom only Î was superior to himself, and so he slew him. Mencius said, 'In this case Î also was to blame. Kung-ming Î indeed said, "It would appear as if he were not to be blamed," but he thereby only meant that his blame was slight. How can he be held without any blame?'

'The people of Chang sent Tsze-cho Yü to make a stealthy attack on Wei, which sent Yü-kung Sze to pursue him. Tsze-cho Yü said, "To-day I feel unwell, so that I cannot hold my bow. I am a dead man!" At the same time he asked his driver, "Who is it that is pursuing me?" The driver said, "It is Yü-kung Sze," on which, he exclaimed, "I shall live." The driver said, "Yü-kung Sze is the best archer of Wei, what do you mean by saying 'I shall live?'" Yü replied, "Yü-kung Sze learned archery from Yin-kung T'o, who again learned it from me. Now, Yin-kung T'o is an upright man, and the friends of his selection must be upright also."

When Yü-kung Sze came up, he said, "Master, why are you not holding your bow?" Yü answered him, "To-day I am feeling unwell, and cannot hold my bow." On this Sze said, "I learned archery from Yin-kung T'o, who again learned it from you. I cannot bear to injure you with your own science. The business of to-day, however, is the prince's business, which I dare not neglect." He then took his arrows, knocked off their steel points against the carriage-wheel, discharged four of them, and returned.
~ James Legge translation via nothingistic.org ~

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