Speech reveals character through the tongue
Nahj al-Balāgha|Volume 1|Book 3|Chapter 392
۳۹۲. وَقَالَ (عليه السلام): تَكَلَّمُوا تُعْرَفُوا، فَإِنَّ الْمَرْءَ مَخْبُوءٌ تَحْتَ لِسَانِهِ.
392. Amīr al-mu’minīn, peace be upon him, said: Speak so that you may be known, since man is hidden under his tongue.