Nahj al-Balāgha
Hadith 1993٤٠. وَقَالَ (عليه السلام) : لِسَانُ الْعَاقِلِ وَرَاءَ قَلْبِهِ، وَقَلْبُ الْأَحْمَقِ وَرَاءَ لِسَانِهِ.
40. Amīr al-mu’minīn, peace be upon him, said: The tongue of the wise man is behind his heart, and the heart of the fool is behind his tongue.