The Shang Dynasty wrote on Oracle Bones. Hope his helps ;)
Answer:
The ban against enslaving Muslims was observed very strictly in Hausaland in many ways. For example. if a non-believer would become a Islamic so called "believer", he would no longer would be someone's possession (slave). This is somewhat illogical because anyone could say that they are a Muslim just to become a free man or woman.
Explanation:
I majored in History