Old Persian religion

Ancient Persian religion was a set of ancient beliefs and practices of the Persian peoples before the rise of Zoroastrianism. The religion closest to it was the historical Vedic religion that was practiced during the Vedic period. The major deities worshipped were Ahura Mazda and Mithra from Iran to Rome, but Atar was also worshipped, as names of kings and common public showing devotion to these three exist in most cases. But some sects, the precursors of the Magi, also worshipped Ahura Mazda, the chief of the Ahuras. With the rise of Zoroaster and his new, reformatory religion, Ahura Mazda became the principal deity, while the Daevas were relegated to the background. Many of the attributes and commandments of Varuna, called Fahrana in Median times, were later attributed to Ahura Mazda by Zoroaster.

The Iranian peoples emerged as a separate branch of the Indo-Iranians in the 2nd millennium BC, during which they came to dominate the Eurasian Steppe and the Persian Plateau. Their religion is derived from Persian religion, and therefore shares many similarities with the Vedic religion of India. Although the Persian peoples left little written or material evidence of their religious practices, their religion is possible to reconstruct from scant Iranian, Babylonian and Greek accounts, similarities with Vedic and other Indo-European religions, and material evidence.

Prior to the Achaemenid period, the daivas were also commonly worshipped. The Achaemenid kings made it a state policy to destroy their shrines and vilify them. Old Persian daiva occurs twice in Xerxes I's daiva inscription (XPh, early 5th century BCE). This trilingual text also includes one reference to a daivadana ("house of the daivas"), generally interpreted to be a reference to a shrine or sanctuary. In his inscription, Xerxes I records that "by the favor of Ahura Mazda I destroyed that establishment of the daivas and I proclaimed, 'The daivas thou shalt not worship!'" This statement has been interpreted either one of two ways. Either the statement is an ideological one and daivas were gods that were to be rejected, or the statement was politically motivated and daivas were gods that were followed by (potential) enemies of the state.

Under the Achaemenids, Ahura Mazda received state patronage as the chief deity and the emperors became his representatives. Ahura Mazda was thus recognized as the creator of the world. Dualism was strongly emphasized and human nature was considered essentially good. The chief ritual of the ancient Iranians was the yasna, in which the deities were praised and the mind-altering drug hauma was consumed. This ritual was performed by a highly trained priestly class. Politics and religion under the Persian empires were strongly connected.

Beginning in the early 10th century BC, the ancient Persian religion was gradually displaced by Zoroastrianism, which contains some aspects of its predecessor.

The sources on ancient Iranian religion, though limited, consist of textual and material sources. The textual sources are both Iranian and non-Iranian.

An important Iranian source is the Avesta, which are Zoroastrian sacred scriptures made in the Avestan language. This is considered the principal source of knowledge on ancient Iranian religions. It is a collection of several texts that seems to have been written over a large span of time by a variety of authors. These texts have been subjected to editings and redactions throughout their development. It is now the only extant fragment of what remained in the 9th century CE of the Avesta compiled in the Sasanian Empire by Khosrow I (6th century CE). Summaries of its content reveal that it was a huge collection containing texts not only in Avestan, but also in Pahlavi, which was the language of Zoroastrianism in the Sasanian Empire. Though the existing Avesta is dated quite recently, it contains information that is considerably older. The Gathas ("Songs") of the Prophet Zoroaster, the Yasnas and much of the Yashts are considered among the oldest. The Gathas includes expressions of the religious vision of Zoroaster, which in many ways is a reinterpretation of the ancient Iranian religious principles. The Yashts are a collection of verses dedicated to various deities. These verses are mostly related to Zoroastrian terminology and ideas, but have little relation to anything specifically Zoroastrian. The gods invoked are basically the pre-Zoroastrian gods of the Iranian peoples. There is little agreement on when Zoroaster lived, but most scholars agree that he lived somewhere between 1200 and 600 BC. Dating the Yashts is similarly difficult, but it is likely that they were redacted (not necessarily composed) initially in the 5th century BC.