"Speak That I May See You"

It’s a strange phrase, but stranger than that is that it's more than true,because while talking, people unconsciously are wide open for others to see, a talking person will reveal who they are, what they like or dislike, their habits, their thoughts, a good listener and a wise one would easily figure out that person in front of him, and may also find out what needs to be done to cheer that person when they're down, or worse they would know how to hurt the person in front of them with the smallest of actions, so whenever you're talking, careful what gets out of your mouth, you never know what the person in front of you is thinking.

And  

"أمير المؤمنين عمر رضى الله قال "المرء مخبوء خلف لسانه