Tishtrya
aka: Tistrya, Tir, Tishtryaeninis, Tishtar

Tishtrya (Tištrya) is the Avestan language name of an Zoroastrian benevolent divinity associated with life-bringing rainfall and fertility. Tishtrya is Tir in Middle- and Modern Persian. As has been judged from the archaic context in which Tishtrya appears in the texts of the Avesta, the divinity/concept is almost certainly of Indo-Iranian origi
n.

As soon as Hormozd (Ahura Mazda) had rested from his creation, he appointed Tishtar to irrigate the world by taking rain from the clouds to drench the land, refresh the plants, open the flowers, fill the rivers with water and make he springs flow and all the Aryan lands prosperous and flourishing.

In the Zoroastrian religious calendar, the 13th day of the month and the 4th month of the year are dedicated to Tishtrya/Tir, and hence named after the entity. In the Iranian civil calendar, which inherits its month names from the Zoroastrian calendar, the 4th month is likewise named Tir.

During the Achaemenid period, Tishtrya was conflated with Semitic Nabu-Tiri, and thus came to be associated with the Dog Star, Sirius. The Tiregan festival, previously associated with Tiri(a reconstructed name), was likewise transferred to Tishtrya. During the Hellenic period, Tishtrya came to be associated with Pythian Apollo, patron of Delphi, and thus a divinity of oracles.