THE YASANA

Yasna 28.1 (Bodleian MS J2)
The Yasna (from yazišn "worship, oblations", cognate with Sanskrit yajña), is the primary liturgical collection. It consists of 72 sections called the Ha-iti or Ha. The 72 threads of lamb's wool in the Kushti, the sacred thread worn by Zoroastrians, represent these sections. The central portion of the Yasna is the Gathas, the oldest and most sacred portion of the Avesta, believed to have been composed by Zarathushtra (Zoroaster) himself. The Gathas are structurally interrupted by the Yasna Haptanghaiti ("seven-chapter Yasna"), which makes up chapters 35-42 of the Yasna and is almost as old as the Gathas, consists of prayers and hymns in honour of the Supreme Deity, Ahura Mazda, the Angels, Fire, Water, and Earth. The structure of the Yasna, though handed down in prose, may once have been metrical, as the Gathas still are.
It is believed by some scholars that the Yasna represents the 21st nask (the seventh and last volume in the third and last group). Six of the nasks from the first group of nasks, which are commentaries on the Gathas, may also be regarded as relevant to the Yasna.
The Yasna, or Izeshne, is primarily the name, not of a book, but of a ceremony in which the entire book is recited and appropriate liturgical actions performed. In its normal form, this ceremony can only be performed in the morning.

THE VISPERAD

The Visperad (from vîspe ratavo, "(prayer to) all patrons") is a collection of supplements to the Yasna. The Visparad is subdivided into 23 or 24 kardo (sections) that are interleaved into the Yasna during a Visperad service (which is an extended Yasna service).
The Visperad collection has no unity of its own, and is never recited separately from the Yasna

THE YASHTS

Faravahar, believed to be a depiction of a Fravashi, as mentioned in the Yasna, Yashts and Vendidad
The Yashts (from yešti, "worship by praise") are a collection of 21 hymns, each dedicated to a particular divinity or divine concept. Three hymns of the Yasna liturgy that "worship by praise" are—in tradition—also nominally called yashts, but are not counted among the Yasht collection since the three are a part of the primary litury. The Yashts vary greatly in style, quality and extent. In their present form, they are all in prose but analysis suggests that they may at one time have been in verse.

THE VENDIDAD

The Vendidad (or Vidēvdāt, a corruption of Avestan Vî-Daêvô-Dāta, "Given Against the Demons") is an enumeration of various manifestations of evil spirits, and ways to confound them. The Vendidad includes all of the 19th nask, which is the only nask that has survived in its entirety. The text consists of 22 Fargards, fragments arranged as discussions between Ahura Mazda and Zoroaster. The first fargard is a dualistic creation myth, followed by the description of a destructive winter on the lines of the deluge of mythology. The second fargard recounts the legend of Yima. The remaining fargards deal primarily with hygiene (care of the dead in particular) [fargard 3, 5, 6, 7, 8, 9, 10, 16, 17, 19] as well as disease and spells to fight it [7, 10, 11, 13, 20, 21, 22]. Fargards 4 and 15 discuss the dignity of wealth and charity, of marriage and of physical effort, and the indignity of unacceptable social behaviour such as assault and breach of contract, and specify the penances required to atone for violations thereof. The Vendidad is an ecclesiastical code, not a liturgical manual, and there is a degree of moral relativism apparent in the codes of conduct. The Vendidad's different parts vary widely in character and in age. Some parts may be comparatively recent in origin although the greater part is very old.
The Vendidad, unlike the Yasna and the Visparad, is a book of laws rather than the record of a liturgical ceremony. However, there is a ceremony called the Vendidad, in which the Yasna is recited with all the chapters of both the Visparad and the Vendidad inserted at appropriate points. This ceremony is only performed at night

THE SIROZA

The Siroza ("thirty days") is an enumeration and invocation of the 30 divinities presiding over the days of the month. (cf. Zoroastrian calendar). The Siroza exists in two forms, the shorter ("little Siroza") is a brief enumeration of the divinities with their epithets in the genitive. The longer ("great Siroza") has complete sentences and sections, with the yazatas being addressed in the accusative.
The Siroza is never recited as a whole, but is a source for individual sentences devoted to particular divinities, to be inserted at appropriate points in the liturgy depending on the day and the month.

THE KHORDEH AVESTA

The Khordeh Avesta ("little Avesta") is both a selection of verses from the other collections, as well as three sub-collections that do not appear elsewhere. Taken together, the Khordeh Avesta is considered the prayer book for general lay use. In a wider sense, the term Khordeh Avesta includes all material other than the Yasna, the Visparad and the Vendidad, as it is only the ceremonies contained in these three books that are reserved for the priests.
The Khordeh Avesta is divided into 4 sections:

1. Five introductory chapters, accompanied by excerpts from different parts of the Yasna.
   


2. Five Niyayishns "praises," addressed to the sun, Mithra, the moon, the waters, and the fire. In the main, the material overlaps with that of the Yashts. The Niyayishn to fire derives from Yasna 62.
   


3. Five Gahs "moments of the day," addressed to the five divisions of the day.
   


4. Four Afrinagans "blessings," each recited on a particular occasion: the first in honor of the dead, the second on the five epagomenal days that end the year, the third is recited at the six seasonal feasts, and the fourth at the beginning and end of summer.