“The tongue is a beast; if it is let loose, it devours.”
“As intelligence increases, speech decreases.”
“Take wise points from wherever they may be, because if a wise saying is in the bosom of a hypocrite it flutters in his bosom till it comes out and settles with others of its own category in the bosom of the believer.”
“The worth of every man is in his attainments.”
“Whoever abandons saying, “I do not know” meets his destruction.”
“I love the opinion of an old man more than the determination of a young man.”
“The hearts get weary as bodies get weary; so look for beautiful wise sayings for them (to dispel their weariness).”
“The lowest form of knowledge is that which remains on the tongue and the most superior form is that which manifests itself through (the action of) the limbs and the organs of the body.”
“When you hear a tradition test it according to the criterion of intelligence not that of mere hearing, because relaters of knowledge are numerous but those who guard it are few.”
“He who acts solely according to his own opinion gets ruined, and he who consults other people shares in their understanding.”
Source: Nahj al-Balagha [The Path of Eloquence]