以公报私yǐ gōng bào sī

假借公事的名义来达到个人的目的：原来这贾瑞最是个图便宜，没行止的人，每在学中～，勒索子弟们请他。(九·204)

以公报私公报私仇yǐ gōng bào sī

use one’s position to gain personal interests; further one’s private ends by means of official resources
❍ 原来这贾瑞最是个图便宜没行止的人，每在学中～，勒索子弟们请他； ……(《红楼梦》111) This Jia Rui was a spineless,unprincipled character who,as a means of obliging the boys to treat him,always displayed the most shameless favouritism in his settlement of classroom disputes.