HALAL AND HARAM (lawful and unlawful things)
(Source: Ihya-Ulum-Id-Din by Imam Ghazzali (r.a.) Revival of Religious Learnings-
English Translation by Fazlul Karim  Publisher Darul-Ishaat Karachi Pakistan)
 

Rasulullah (sallallaho alaihe wasallam) said : It is compulsory on every Muslim to seek lawful earnings. He termed this compulsory subject as a thing of wisdom for a wise man out of other compulsory things. Lawful things are clear and unlawful things are also clear. between these two , there are doubtful things which are not clear and difficult to know. All things are limited within these three things.

MERITS OF LAWFUL EARNINGS AND CONDEMNATION OF UNLAWFUL

In Holy Quran Allah says: