You're looking for this I believe:
ISLAMIC CASTE:
Any of the units of social stratification that developed between Muslims in India and Pakistan as a result of the proximity of Hindu culture.Much of the
South Asian Muslims were recruited from the Hindu population;despite the egalitarian tenets of Islam,the Muslim converts persisted in their Hindu social habits.Hindus,in turn,accommodated the Muslim ruling class by giving it a status of its own. In South Asian Muslim society a distinction is made between the "ashraf"(Arabic,plural of sharif, "nobleman" ),who are supposedly descendants of Muslim Arab immigrants,and the "non-ashraf",who are Hindu converts.
The "ashraf" group is further subdivided into four subgroups:
1)Sayyids,originally a designation of descendants of Muhammad through his daughter Fatimah and son-in-law 'Ali,
2)Shaykhs(Arabic-"Chiefs" ),mainly descendants of Arab or Persian immigrants but also including some converted Rajputs,
3)Pashtuns,member of the Pashto-speaking tribes in Afghanistan and north western Pakistan,and
4)Mughal,persons of Turkish origin,who cam into India with the Mughal armies.
The "non-ashraf" Muslim castes are of three levels of status:
1)at the top,converts from high Hindu castes,mainly Rajputs,insofar as they have not been absorbed into the Shaykh castes;
2)next the artisan caste groups,such as the Julahas,originally weavers;
3)and lowest,the converted untouchables,who have continued their old occupations.These converts of Hinduism observe endogamy in a manner closer to their Hindu counterparts.
Two of the principal indexes of Hindu caste,commensality and endogamy(principles governing eating and marital arrangements),do not appear as strongly in Islamic castes.Commensality is prohibited between ashraf and non-ashraf,between Muslim and Hindu,and between the various castes of the non-ashraf.
The principle of endogamy is altered by the Muslim preference of marriage within very narrow limits(eg, to the daughter of the father's brother),which in South Asia is known as "biyadhari".