“Abu ‘Abd Allah (a.s.), has said that once a man came to ’Amir al-Mu’minin saying, ‘In my earnings I have been neglectful about lawful and unlawful matters, and I want to repent, but I do not know which item in my possession is lawful and which is not.’ ‘Amir al-Mu’minin (a.s.), said, ‘Give one-fifth of your assets in charity. Allah, most Glorious is whose name, accepts one-fifth of things. The rest of your assets are lawful for you.’”