A closed community forbidding conversion and intermarriage

Parsi and Irani Zoroastrians characteristically affirm that the community is closed, that Zoroastrian identity passes by birth to the children of Zoroastrian parents, and that conversion and, in the stricter view, marriage outside the community are not accepted. On this understanding one is born a Zoroastrian rather than becoming one, and the faith is preserved within the descent group. The position is bound up with the small community's long experience as a minority and with its concern to maintain religious and, for many, ethnic continuity.

The community's closed character is bound up with its own founding narrative: the Qissa-i Sanjan, a sixteenth-century Persian-language account of much earlier events, describes Zoroastrian refugees fleeing the Arab Muslim conquest of Persia and arriving by sea on the coast of Gujarat, where the local ruler is said to have granted them refuge on condition that they adopt local language and dress while retaining their own religion, a story often illustrated by the image of sugar dissolved into a full cup of milk, sweetening it without causing it to overflow. Historians treat the text's precise dating and details as legendary rather than a strict historical record, but the Parsi community has long drawn on the story to explain both its integration into Indian society and its determination to preserve religious boundaries around that integration.

The closed-community stance has become a matter of internal debate, especially in the diaspora, as intermarriage rises and numbers decline; more liberal voices question the traditional prohibitions while traditionalists hold them essential to the faith's survival. The practice distinguishes Zoroastrianism from the actively missionary traditions and reflects its character as the religion of a particular, historically rooted people. It applies among both the Parsis of India and the Iranian Zoroastrians, though communities and individuals differ in how strictly they maintain it.

The boundary has produced real, documented legal conflict in modern India: a 1908 Bombay High Court ruling in a dispute generally known as the Parsi Panchayat case held that children of Parsi fathers and non-Parsi mothers could be considered Parsi while children of Parsi mothers and non-Parsi fathers generally could not, a gendered asymmetry that has remained contentious and been challenged repeatedly in Indian courts and Parsi community bodies into the twenty-first century, with some fire temples and community trusts continuing to restrict access on this basis while individual reformers and several court petitions have pushed for a more inclusive definition of who counts as a Zoroastrian by birth.