In written sources (including anecdotes and Daoist liturgical texts), this taboo first appeared in the 9th to 12th centuries (Tang-Song transition, with the advent of pork meat.) By the 16th to 17th centuries, the beef taboo had become well accepted in the framework of Chinese morality and was found in morality books (善書), with several books dedicated exclusively to this taboo. The beef taboo came from a Chinese perspective that relates the respect for animal life and vegetarianism (ideas shared by Buddhism, Confucianism, and Daoism, and state protection for draught animals.) In Chinese society, only ethnic and religious groups not fully assimilated (such as the Muslim Huis and the Miao) and foreigners consumed this meat. This taboo, among Han Chinese, led Chinese Muslims to create a niche for themselves as butchers who specialized in slaughtering oxen and buffalo.