It is confirmed that one of the Companions addressed his tongue by saying:

يَا لِسَانُ قُلْ خَيْراً تَغْنَمْ وَاسْكُتْ عَنْ شَرٍّ تَسْلَمْ مِنْ قَبْلِ أَنْ تَنْدَمَ، إِنِّي سَمِعْتُ رَسُولَ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ: "أَكْثَرُ خَطَايَا ابْنِ آدَمَ مِنْ لِسَانِهِ"

 Ya lisanu qul khayran taghnam waskut ^an sharrin taslam min qabli an tandam. Inni sami^tu Rasulallahi, sallallahu ^alayhi wa sallam, yaqul: Aktharu khatayabni Adama mil-lisanih.

Which means: “O tongue, say what is good and you will gain, and keep silent about what is bad before you regret it. I heard the Messenger of Allah saying: ‘Most of the human’s sins are from his tongue.’ ” Related by at-Tabaraniyy.

 1-    Gossip (Ghibah): Means to mention a matter related to a Muslim in his absence in a way that he hates. If a Muslim person was short, and hated for that to be said about him, and someone else said in his absence, so and so is short, then this is considered among the unlawful gossip that the Prophet prohibited.