Avesta is a collection of ancient Persian sacred books compiled in the first half of the 1st millennium BC. e., is used as religious texts of Zoroastrianism. The history of the composition of the Avesta texts remains largely unclear; one can only assume that in Seleucid and early Parthian times there was no written canon of the Avesta. In Zoroastrian communities, only individual Yashts were preserved (and edited). Their analysis reveals a certain syncretism inherent in that time. A study of the texts leads to the conclusion that over the course of thousands of years, the theoretical views and moral views set forth in the Avesta have changed. The content of later parts introduced many changes into the original teaching.