Hystaspes (OP. Vištâspa): name of several noble Bactrians. One of them is mentioned in the Avesta, the holy book of Zoroastrism, the Bactrian religion that was founded by the legendary prophet Zarathustra.
Vištâspa, the son of Aurvat-aspa, was the king of a country that has been identified with Chorasmia and Aria; since he was a contemporary of Zarathustra, he may have lived in the fourteenth or thirteenth century BCE.
According to Avestan history, Vištâspa offered asylum to Zarathustra when the latter was hunted down by his opponents, the priests of the god Mithra. Later, the king organized a debate between the prophet and the priests; when Zarathustra had proved that his doctrines were superior, Vištâspa became an adherent of the new religion. Legend has elaborated this story and added an intervention by Ahuramazda in person (click here).
The cypress at Kâshmar is said to have been the tree under which the debaters argued, but when this tree was cut down in 838 CE, it was discovered that it had 1450 rings, which suggests that it was planted centuries after the religious debate.
One of the Yashts, Avestan hymns to lower deities, is said to have been written by Vištâspa, but this is almost certainly untrue. In the first centuries CE, a book of Oracles of Hystaspes was very popular in the Roman Empire; it was probably written by a Magian who used Avestan texts and elements from the Persian folk lore, and describes the end of the world.
Vištâspa is not to be confused with Hystaspes, the father of the Persian king Darius the Great.