Amir al-mu'minin, peace be upon him, said: Knowledge is a venerable estate; good manners are new dresses; and thinking is clear mirror.Amir al-mu'minin, peace be upon him, said: Whenever a person conceals a thing in his heart it manifests itself through unintentional words from his tongue and (in) the expressions of his face.Amir al-mu'minin, peace be upon him, said to his son al- Hasan:

O' my son, learn four things and (a further) four things from me. Nothing will harm you if you practise them. That the richest of riches is intelligence; the biggest destitution is foolishness; the wildest wildness is vanity and the best achievement is goodness of the moral character.

O' my son, you should avoid making friends with a fool because he may intend to benefit you but may harm you; you should avoid making friends with a miser because he will run away from you when you need him most; you should avoid making friends with a sinful person because he will sell you for nought; and you should avoid making friends with a liar because he is like a mirage, making you feel far things near and near things far.