先小人，后君子

Explanation: Do first villain, after doing a gentleman. First thought to the interests of gains and losses that the words in front, and then revisit the friendship. 　　Source: Qing Zhou students "Belief and" back of the 49th say. Where are generous well in advance, after the first gentleman villain on the bad. " 　　Examples: Let ~. Help, I can give a room the money. ★ Qing Shi Yukun "San Xia Wu Yi," the 32nd back