I say: The "Principal Capitals" (Ru’us al-Amwal)—whose origin is lawful—are the Inward Knowledge (Al-‘Ilm al-Batin), which neither increases nor decreases. The Almighty does not accept any addition to it from elsewhere, nor any subtraction from it, as stated in the third chapter of Ecclesiastes (Al-Jami‘a): "I know that everything God does will endure forever; nothing can be added to it and nothing taken from it."1
Bahlul ibn ‘Umar al-Kufi—peace be from him—said: "Eat all the food and stick to silence." Its meaning is: Believe in the Inward Knowledge and conceal it from those who are not its people, for "silence" here signifies concealment (Kitman). And Allah knows best.
Our Master, Amir al-Mu’minin [Ali ibn Abi Talib]—from him be mercy—pointed to this meaning in Nahj al-Balagha when mentioning the world, saying: "Depart from it [the world] with the best of the provision (Al-Zad) you have at hand; do not ask therein for more than what is sufficient (Al-Kafaf), and do not seek from it more [than...] [more than] what is sufficient (Al-Balagh)."