Imam Ali (peace be upon him): Allah, Blessed and Exalted, revealed the Quran in seven categories, each of which is healing and sufficient. Those seven categories are: command, prohibition, encouragement, warning, disputation, parable, and stories. Command and prohibition are in one direction, for there is no meaning among the meanings of command except that a prohibition comes after it, and there is no kind of prohibition except that a command comes with it. Allah the Exalted has said: یا أَیُّهَا الَّذِینَ آمَنُوا اسْتَجِیبُوا لِلهِ وَ لِلرَّسُولِ إِذا دَعاکُمْ لِما یُحْیِیکُمْ [O you who believe! Answer (the call of) Allah and His Messenger when he calls you to that which gives you life]. Through this verse, Allah has informed us that the servants do not live except through command and prohibition.