From the dawn of history the Indo Europeans, especially the ancient Iranians have celebrated the horse in their art and in their literature. Avestan hymns abound with praises of the horse (Swift horses were among the most desired boons bestowed by aši, the ahûrá god-being of wealth, prosperity (Yašt 17.12.)
The myth of the Sun’s horse-drawn chariot is wide spread among Indo-European people. In the sacred lore of the Zoroastrians, the Avestá, the myth of the Sun’s horse-drawn chariot is retold in the hymn to Mithrá.
“Four speedy (white horses,) undying, reared on spiritual/mental food (mainyuuš xvarəθa), the fore hooves shod with gold, their hind hooves with silver” draw the chariot of Mithrá (Yašt 10.125.)
Mithrá embodies the “Invincible powers of light, including the Invincible Sun,” and “friendship with the Gods.”
Similarly, Odin and other Norse gods ride horses. Their horses are immortal, like Mithra’s steeds, having been reared on mental/spiritual food (mainyuuš xvarəθa) that never weary or die.
In the Avestan hymns, Vərəθraγna (the beloved ahûrá of victory) and Tištriya (Tri star, Sirius) both take form in the shape of a bright, white horse, among other astrological representations (Yast 149; 8.18.)
Also, four white horses draw the chariot of Sraôšá (Yasna 57.27.) Sraôšá is “divine Inspiration, the call of the Immortals to overcome limitations, and achieve everlasting glory, and good fame.”
Chariot imagery appears twice in the poetic gathas of Zarathustra, We read in Yasna 50.6:
He who gives superior wisdom to be the charioteer of my tongue// teach me his sacred formulas with good spirit/mind//I will yoke you the swiftest steeds, ones widely victorious in your laudation//Mindful Lord, in excellence/truth, powerful with good spirit/mind//ride ye with them, and bring Me divine favor, luck.
At Yasna 30.10, the seer/prophet declares: that “when luminous vision triumphs, the swiftest (steeds) will be yoked from the fair, brilliant dwelling of good spirit/mind of the Mindful lord, and of excellence/truth, and they will win good fame.”
Among the Greek poets, the horse-drawn chariot is identified as that of the Muse or Muses which shows a strong parallel to the last gathic verses as well as the account of the horse drawn chariot of sraôšá “divine Inspiration” in the Avesta.
Both Vedic and Celtic poets were rewarded with gifts of horses and cattle, whereupon the patron of the poet received further praise for his liberality. Likewise, in Yasna 44.18, seer/prophet Zarathustra talks about his reward of ten mares with stallion and an aurochs/camel.
The honored position of the horse in the Avestan lore is underlined by the fact that many notable Avestan heroes—including prophet Zarathustra’s forebears—and patron Vištaspá bore names compounded with aspá-“horse.”
Avestan aspá “horse” is a cognate of Vedic ášva, Old Prussian aswinan, Lithuanian ašvîenis, Greek híppos, Luwian azuwa, Lycian esbe, Modern Persian asb, Old Latin equos, Hittite *ēkkus, all going back to reconstructed Proto Indo European *ék̑wos.
In the ancient Germanic Futhark alphabet, rune *ehwaz “horse” comes from the same ancient Aryan root.
The word for “horse” in ancient Indo European speech is connected with the word for “swift” e.g. Avestan ásü aspá “swift horses” or Vedic term áśvāh āšávah. Thus the word for “horse” designated or meant originally “the swift one.”
The Vedic ašvín “divine horses” were notable for their constant travelling between the realm of Immortals and mortals (RV 7. 67. 8.)
In the imagery of horses and Sun’s chariot, we find the idea that the sacred song/hymn makes swift movement between the boundless, brilliant realm of Immortals and limited world of men possible.
In the Avesta, the patron deity of horses is called Drváspá “possessing strong, healthy horses.” Strict rules are prescribed by the Avesta concerning the breeding, grooming, training, and feeding of horses, and guarding them from diseases and harm, (see, e.g. *Duzd-sar-nizad Nask as summarized in Dēnkard 8.24. and Nikátüm in Nask, 8.19, 40).
I like to conclude with An Old English rune poem:
Eh byþ for eorlum æþelinga wyn,
hors hofum wlanc, ðær him hæleþ ymb[e]
welege on wicgum wrixlaþ spræce
and biþ unstyllum æfre frofur.
The horse is a joy to princes in the presence of warriors, / a steed in the pride of its hoofs, / when rich men on horseback bandy words about it; / and it is ever a source of comfort to the restless.