Yes, it is compulsory. Islamic law is currently not recognised in South Africa and if there is no Islamic will, or any will for that matter, the Intestate Succession Act would govern the administration of the estate. The Prophet Mohammed, may peace be upon him, stated that it is unlawful for a Muslim to let three nights go by without drafting a will. This underscores the importance of a will in the Islamic faith. If you live in a country that does not recognise Islamic inheritance law, then the aforementioned hadith would be even more relevant to you.