Mencius - Book 4, Part 2, Chapter 23

Mencius said, 'When it appears proper to take a thing, and afterwards not proper, to take it is contrary to moderation. When it appears proper to give a thing and afterwards not proper, to give it is contrary to kindness. When it appears proper to sacrifice one's life, and afterwards not proper, to sacrifice it is contrary to bravery.'
~ James Legge translation via nothingistic.org ~

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