 For Zoroastrian laypersons, the distinction between the two groups was at best theoretical and by the 10th century, the term "hērbad" had lost most associations of scholarship and eventually came to refer to priests that had no theological authority.Beyond that distinction, the terms "hērbad", "mobad" and "dastūr" were used interchangeably.In the 16th century, the "Rivayat" epistles encouraged the Indian Zoroastrians to distinguish between priests capable of officiating at a "Vendidad" reading and the others.