Those who know say nothing

A father tells his children that sometimes things people know may never be put in words. But on the other hand, most would put so many words about things they don’t now. He says that knowing the difference is a sign of wisdom. And he tells them this:
“Those who know do not say. But those who say do not know.”
“Wow! That’s deep. What do you mean by that, dad?”
“Do you know the fragrance of a rose?” he asks.
They all know.
He says, “Now put it in words.”
All are silent.