Nahj al-Balagha Hadith n. 301

Selections from The Sayings and Preaching of Amir al-Muminin Ali ibn Abi Talib (Peace Be Upon Him) Including His Replies to Questions and Maxims Expressed for Various Purposes.
Translated by Sayyid Ali Reza

وَقَالَ (عليه ‏السلام):

Amir al-mu'minin, peace be upon him, said:

رَسُولُكَ تَرْجُمَانُ عَقْلِكَ،

Your messenger is the interpreter of your intelligence

وَكِتَابُكَ أَبْلَغُ مَا يَنْطِقُ عَنْكَ.

while your letter is more eloquent in expressing your true self.