there's no smoke without fire idiom UK saying (US where there's smoke, there's fire)
无火不冒烟;无风不起浪
If unpleasant things are said about someone or something, there is probably a good reason for it.
She says the accusations are not true, but there's no smoke without fire. 她说那些指控纯属子虚乌有，但无风不起浪。