The Zoroastrian scripture containing priestly laws is the Videvdad.
Also known as the Vendidad or Vidēvdād, it is an Avestan text devoted largely to religious law, ritual purity, pollution, funerary practice, and rules intended to repel demonic forces. Its title is generally interpreted as “Law for Repelling the Demons,” reflecting its concern with protecting the good creation from impurity and disorder.
The surviving text contains 22 chapters, traditionally called fragards. Some sections address contracts, assault, punishment, and social conduct, but much of the work focuses on purity regulations, including responses to contact with corpses and other sources of pollution. Videvdad is not the Bundahishn, which explains cosmology; nor is it the Khorda Avesta, a collection of shorter prayers, or the Yashts, hymns to individual divinities. “Vendidad” is the most familiar English spelling, but “Videvdad” is a valid scholarly form.