From the book Minorities in the Arab World , A.H. Hourani. Oxford University Press, 1947.  

These are religious minorities that have resided in Egypt, Palestine, Lebanon, Syria and Iraq, or in other parts of  the     Middle East before coming to these countries, and are nationals of these countries,  are Sunni but not Arabic speaking, and  others again that are neither Sunni not Arab.

(1) The Yazidis are at times defined as “devil worshippers”, but this is inaccurate. They regard Satan as the fallen angel who will some day be reconciled with God, and take considerable pains to propitiate him. They symbolize him as a sacred peacock. They regards the Old and New Testaments and the Quran as Sacred Books, and their rites show signs of Christian, Muslim and Magian influences. They are a racial as well as a religious minority, being probably of Kurdish origin. The speak a Kurdish dialect, but use Arabic in their rites. The center of their religion is at Sheikh Adi, north of Mosul.

(2) The Mandeans are also known as Sabaeans or Christians of St John. The doctrines of their religions are not very different from those of Islam, with certain accretions form other religions. Although they speak Arabic in daily life, they use a distinctive language for liturgical and other religious purposes. Ritual ablutions play an important part in the practice of their faith, which also enjoins upon them vegetarianism and pacifism.

(3) The Shabak are a community of Kurdish origin who live in the same area as the Yazidis and are not clearly differentiated form them. Their religion is compounded of Yazidi and extreme Shi'i elements.

(4) The Baha'is profess the doctrine first expounded by a Persian religious reformer, the Bab, in 1844 and amplified by his successor. Persecuted in Persia, they transferred their headquarters to Palestine and sent out missionaries as far as America. The greta majority of Baha'is is still in Iran. They believe in a progressive and unending succession of revelations, each leading man nearer to the incomprehensible nature of God; but on the whole their preaching is directed more towards ethics than the elaboration of a systematic theology.