Ancient Iranian religion was strongly connected. Beginning in the early 10th-century BC, the ancient Iranian religion was gradually displaced by Zoroastrianism, which contains many essential 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. This is considered the principal source of knowledge on ancient Iranian religions. It is a collection of several texts that seems to have been over a large span of time by a variety of authors. These
Avesta the extended Yasna are from the "Yasht"s, which are hymns to the individual "yazata"s. Unlike the "Yasna", "Visperad" and "Vendidad", the "Yasht"s and the other lesser texts of the Avesta are no longer used liturgically in high rituals. Aside from the "Yasht"s, these other lesser texts include the "Nyayesh" texts, the "Gah" texts, the "Siroza", and various other fragments. Together, these lesser texts are conventionally called "Khordeh Avesta" or "Little Avesta" texts. When the first "Khordeh Avesta" editions were printed in the 19th century, these texts (together with some non-Avestan language prayers) became a book of common prayer for lay