The Bible instructs us on this subject in Luke 6:45. “The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks.”
The instruction is a wise one. It reminds us that what is in the heart comes out in words. So the lesson really is to tend to your heart. Fill it with love and kindness and generosity. Then your mouth will speak only what is in the heart.
I am struck by this Arabic proverb: “Open your mouth only if what you are going to say is more beautiful than silence.” That is wise advice worthy to be heeded. If I speak, will my words share beauty with those who hear? Or is it better for me to be silent?