明人不作暗事 míngrén bù zuòànshì
[fair,an honest man does not engage in clandestine dealings;an honest person will do nothing underhand] 正直的人不干不可告人的勾当
你且喝一杯热酒暖暖寒,明人不做暗事,叫你死而无怨。——《三侠五义》