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 year, the third is recited at the six seasonal feasts, and the fourth at the beginning and end of summer. All material in the "Avesta" that is not already present in one of the other categories falls into a "fragments" category, which – as the name suggests – includes incomplete texts. There are altogether more than 20 fragment collections, many of which have no name (and are then named after their owner/collator) or only a Middle Persian name. The more important of the fragment collections are the "Nirangistan" fragments (18 of which constitute the "Ehrbadistan"); the "Pursishniha" "questions," also known