英thief in the family is difficult to detect; a thief from within is hard to guard against; it is difficult to forestall a thief within the house;
引《五灯会元·同安志禅师法嗣·梁山缘观禅师》：“问：‘家贼难防时如何？’师曰：‘识得不为寃。’”
清 李渔 《凰求凤·悟奸》：“这等看起来，真箇是家贼难防，连星相医卜的话都是他教导的了？”
引《五灯会元·卷一四·同安志禅师法嗣》：「问：『家贼难防时如何？』师曰：『识得不为冤。』」