When someone gives you information that is a rumor or not accurate, you should “take it with a grain of salt”. In other words, until you know the facts, you should be doubtful.
Some word experts think this expression first appeared in Latin by a Roman scholar in the 1st century B.C. The report was of the discovery of an antidote to poison: Take it with a grain of salt (cum grano salis). Perhaps the saying refers to food that’s not so tasty (like a story that’s not so believable) being swallowed a little more easily with a little salt. Another possibility is that a single grain of salt isn’t worth much, just like a story you don’t think is completely true.
Here is the idiom being used in a sentence:
Old Mr. Roper tends to exaggerate the stories that he tells. Take his stories with a grain of salt.