Nahj al-Balāgha

Hadith 1684
governance
٦٠. وَقَالَ (عليه ‏السلام): الِّلسَانُ سَبُعٌ، إِنْ خُلِّيَ عَنْهُ عَقَرَ.
60. Amīr al-mu’minīn, peace be upon him, said: The tongue is a beast; if it is let loose, it devours.
Source: al-Sharīf al-Raḍī