Mencius - Book 2, Part 1, Chapter 2F

Ch'âu said, 'Formerly, I once heard this: Tsze-hsiâ, Tsze-yû, and Tsze-chang had each one member of the Sage. Zan Niû, the disciple Min, and Yen Yüan had all the members, but in small proportions. I venture to ask, With which of these are you pleased to rank yourself?'

Mencius replied, 'Let us drop speaking about these, if you please.'

Ch'âu then asked, 'What do you say of Po-î and Î Yin?' 'Their ways were different from mine,' said Mencius. 'Not to serve a prince whom he did not esteem, nor command a people whom he did not approve; in a time of good government to take office, and on the occurrence of confusion to retire: this was the way of Po-î. To say "Whom may I not serve? My serving him makes him my ruler. What people may I not command? My commanding them makes them my people."

'In a time of good government to take office, and when disorder prevailed, also to take office: that was the way of Î Yin. When it was proper to go into office, then to go into it; when it was proper to keep retired from office, then to keep retired from it; when it was proper to continue in it long, then to continue in it long - when it was proper to withdraw from it quickly, then to withdraw quickly: that was the way of Confucius. These were all sages of antiquity, and I have not attained to do what they did. But what I wish to do is to learn to be like Confucius.'
~ James Legge translation via nothingistic.org ~

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