Classical-flavoured set phrase:
非 'if not' +
诚 'sincere' +
勿 'don't' +
扰 'disturb' → 'if not sincere, do not disturb'. Standard at the end of personal ads, rental listings, and selling posts. Jiangsu TV borrowed it as the title for its matchmaking show; Feng Xiaogang's 2008 film used it first in pop culture.