Mencius - Book 5, Part 2, Chapter 3A

Wan Chang asked Mencius, saying, 'I venture to ask the principles of friendship.' Mencius replied, 'Friendship should be maintained without any presumption on the ground of one's superior age, or station, or the circumstances of his relatives. Friendship with a man is friendship with his virtue, and does not admit of assumptions of superiority.

'There was Mang Hsien, chief of a family of a hundred chariots. He had five friends, namely, Yo-chang Chiû, Mû Chung, and three others whose names I have forgotten. With those five men Hsien maintained a friendship, because they thought nothing about his family. If they had thought about his family, he would not have maintained his friendship with them.
~ James Legge translation via nothingistic.org ~

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