there is no smoke without fire 无风不起浪；无火不生烟,谣言总是事出有因。

【例句】
An old adage says: "There is no smoke without fire."
古老的谚语说：“无风不起浪。”

No smoke without fire. (There is no smoke without fire.)
无火那有烟。无风不起浪。事出必有因。