Messengers as interpreters and letters as true expressions
Nahj al-Balāgha|Volume 1|Book 3|Chapter 301
٣٠١. وَقَالَ (عليه السلام): رَسُولُكَ تَرْجُمَانُ عَقْلِكَ، وَكِتَابُكَ أَبْلَغُ مَا يَنْطِقُ عَنْكَ.
301. Amīr al-mu’minīn, peace be upon him, said: Your messenger is the interpreter of your intelligence while your letter is more eloquent in expressing your true self.