רְאוּבֵן֙ בְּכֹ֣רִי

via Lma’an Yishme’u

Since the power of speech is an expression of the Shechina within a person, one must try to use it forholy purposes. For this reason, the tongue is hidden in the mouth, just as a treasure is kept concealed and locked. (ראשית חכמה שער הקדושה פי"א)