[21] In the Sermon of Amir-ul-Momineen -asws (Khutba Al-Waseela)...
There is no wealth more valuable than the intellect, and no poverty which is more intense than the ignorance, and no preacher which is more profound than the sound advice, and no reasoning like the Taffakur (contemplation), and no worship like the pondering, and no demonstration more reliable than the consultation, and no isolation more severe than the self-conceit, nor piety like refraining from the Prohibitions, and no forbearance like patience and silence.
There are witnesses for the hearts which hold them back from being the people of excesses, and there is insight for the understanding, which alerts the self and caution it from the danger. And for the heart there are memories of desires, and the intellect admonishes and prohibits from it. And in the experiences there is an appellant, which is a reliable guide to the right way.
It is sufficient for yourself what you would not like it to happen to others, and it is upon you that the same should be for your believing brother, and in it upon him, likewise. The one who considers his own opinion to be self-sufficing from him would endanger him, and the pondering before the deeds would keep you safe from remorse. And the one who welcomes different opinions would understand the places of mistakes.