A peculiar and interesting use of the instrumental case of the word sattā, which seems to have escaped the attention of the Sanskrit dictionaries, occurs frequently in the legal and commentatorial literature in connection with the Brahmanical gotra-system. Briefly, the situation is as follows: a Brahman may not marry within his own gotra. But as the word gotra came in the course of linguistic development to be loosely applied to subdivisions of the original groups, and even to individual families, while the exogamous unit remained the larger group, the prohibition of marriage within the gotra became ambiguous, and required to be supplemented, or rather defined, by a consideration of the pravara, the list of ṛṣi-names recited on specific sacrificial occasions. In other words, the pravara is used as a test to decide to which of the large exogamous groups a man belongs. In the pravara-appendix to the Baudhāyana Śrauta Sūtra the rule reads: eka eva ṛṣir yāvat pravareṣv anuvartate, tāvat samānagotratvam anyatra bhṛgvaṅgirasāṃ gaṇāt. “If even one ṛṣi recurs in the pravaras, that constitutes sameness of gotra (for exogamous purposes), except in the case of a gaṇa of the Bhṛgus and Aṅgirases (where a majority of the ṛṣi-names must be identical in order to prevent intermarriage).” Thus, for example, a member of the Nidhruva “gotra”, with the pravara “Kāśyapa, Āvatsāra, Naidhruva”, and a member of the Śaṇḍila “gotra”, with the pravara “Kāśyapa, Āvatsāra, Śāṇḍila”, both clearly belong to the Kaśyapa gotra, and as such are forbidden to marry.