What Is The Secret of Sarah's Greatness?

"And Sarah was listening from inside the tent." (18:10)
​This is the model for all the behavior of Sarah. 1) She always kept out of sight. 2) She always stood near the doorway to listen to Abraham's discourses to wayfarers and others, in which he spoke of G-d's ways and of virtue and wisdom. The verse really states " Sarah was a listener," and thereby she attained greatness. -- The Beginning