Hazrat Mufti Ebrahim Salejee (Daamat Barakaatuhu) mentioned:
Aspects of halaal and haram are extremely important. Someone asked Imaam Muhammad (rahmatullahi ‘alaih), the leading student of Imaam Abu Haneefah (rahmatullahi ‘alaih) that why have you not written any kitaab on tasawwuf, whereas you have written many kitaabs? He replied that the purpose of tasawwuf is to cleanse oneself and strenghten the connection with Allah Ta‘ala, and this is based on one’s consumption of halaal and haraam. Hence, I have written a book on business dealings since every person is engaged in some type of business which then gets him involved in halaal and haraam. Thus, how important it is to get our business dealings in order.