Gayatri Pariwar have been organising performances of a modernised version of the sacrifice, not involving actual animal sacrifice, since 1991.
The horse to be sacrificed must be a stallion, more than 24, but less than 100 years old. The horse is sprinkled with water, and the Adhvaryu and the sacrificer whisper mantras into its ear. Anyone who should stop the horse is ritually cursed, and a dog is killed symbolic of the punishment for the sinners. The horse is then set loose towards the North-East, to roam around wherever it chooses, for the period of one year (or half a year, according to some commentators). The horse is associated with the Sun, and its yearly course. If the horse wanders into neighbouring provinces hostile to the sacrificer, they must be subjugated. The wandering horse is attended by a hundred young men, sons of princes or high court officials, charged with guarding the horse from all dangers and inconvenience. During the absence of the horse, an uninterrupted series of ceremonies is performed in the sacrificer's home.
After the return of the horse, more ceremonies are performed. The horse is yoked to a gilded chariot, together with three other horses, and RV 1.6.1,2 (YV VSM 23.5,6) is recited. The horse is then driven into water and bathed. After this, it is anointed with ghee by the chief queen and two other royal consorts. The chief queen anoints the fore-quarters, and the others the barrel and the hind-quarters. They also embellish the horse's head, neck, and tail with golden ornaments. The sacrificer offers the horse the remains of the night's oblation of grain.
After this, the horse, a hornless he-goat, a wild ox (go-mrga, Bos gavaeus) are bound to sacrificial stakes near the fire, and seventeen other animals are attached to the horse. A great number of animals, both tame and wild, are tied to other stakes, according to a commentator 609 in total (YV VSM 24 consists of an exact enumeration).
Then the horse is slaughtered (YV VSM 23.15, tr. Griffith)
The chief queen ritually calls on the king's fellow wives for pity. The queens walk around the dead horse reciting mantras. The chief queen then has to mimic copulation with the dead horse, while the other queens ritually utter obscenities.
On the next morning, the priests raise the queen from the place where she has spent the night with the horse. With the Dadhikra verse (RV 4.39.6, YV VSM 23.32), a verse used as a purifier after obscene language.
The three queens with a hundred golden, silver and copper needles indicate the lines on the horse's body along which it will be dissected. The horse is dissected, and its flesh roasted. Various parts are offered to a host of deities and personified concepts with cries of svaha "all-hail". The Ashvastuti or Eulogy of the Horse follows (RV 1.162, YV VSM 24.24–45), concluding with:
The priests performing the sacrifice were recompensed with a part of the booty won during the wandering of the horse. According to a commentator, the spoils from the east were given to the Hotar, while the Adhvaryu a maiden (a daughter of the sacrificer) and the sacrificer's fourth wife.
The Shatapatha Brahmana emphasizes the royal nature of the Ashvamedha:
A historically documented performance of the Ashvamedha is during the reign of Samudragupta I (d. 380), the father of Chandragupta II. Special coins were minted to commemorate the Ashvamedha and the king took on the title of Maharajadhiraja after successful completion of the sacrifice.
There were a few later performances, one by Raja of Kannauj in the 12th century, unsuccessfully, as Prithviraj Chauhan thwarted his attempt and later married his daughter. The last known instance seems to be in 1716 CE, by Jai Singh II of Amber, a prince of Jaipur
In the Mahabharata, the sacrifice is performed by Yudhishtira (Book 14), his brothers guarding the horse as it roamed into neighbouring kingdoms. Arjuna defeats all challengers. The Mahabharata says that the Ashvamedha as performed by Yudhishtira adhered to the letter of the Vedic prescriptions. After the horse was cut into parts, Draupadi lies beside the slain animal (14.89).
In the Ramayana, Rama's father Dasharatha performs the Ashvamedha, which is described in the bala kanda (book 1) of the poem. The Ramayana provides far more detail than the Mahabharata. Again it is stated that the ritual was performed in strict compliance with Vedic prescriptions (1.14.10). Dasaratha's chief wife Kausalya circumambulates the horse and ritually pierces its flesh (1.14.33). Then "Queen Kausalya desiring the results of ritual disconcertedly resided one night with that horse that flew away like a bird." [1-14-34]. At the conclusion of the ritual Dasharatha symbolically offers his other wives to the presiding priests, who return them in exchange for expensive gifts (1.14.35).
The ritual is performed again towards the end of the poem, but in very different circumstances. It figures centrally in the uttara kanda (book 7) where it leads to the final major story in the poem. In this narrative, Rama was married to a single wife, Sita, who at the time was not with him, having been excluded from Rama's capital of Ayodhya. She was therefore represented by a statue for the queen's ceremony (7.x). Sita was living in Valmiki's forest ashram with her twin children by Rama, Lava and Kusha, whose birth was unknown to Rama. In its wanderings, the horse, accompanied by an army and Hanuman, Rama's monkey-devotee enters the forest and encounters Lava, who ignores the warning written on the horse's headplate not to hinder its progress. He tethers the horse, and with Kusha challenges the army, which is unable to defeat the brothers. Recognising Rama's sons, Hanuman sends them to Ayodhya where they are reconciled with their father, who also accepts Sita back at court. Sita, however, no longer wishes to live, and is absorbed by the earth. It is never stated whether the sacrifice was completed, but after Sita's death Rama is said to have repeatedly performed the Ashvamedha using the golden statue as a substitute for his wife.
Some historians believe that the bala kanda and uttara kanda were latter interpolations to the authentic form of the Ramayana, due to references to Greek, Parthians and Sakas, dating to no earlier than the 2nd century BCE
The Gaulish personal name Epomeduos is from *ek'wo-medhu- "horse+mead", while ashvamedha is either from *ek'wo-mad-dho- "horse+drunk" or *ek'wo-mey-dho- "horse+strength". The reconstructed myth involves the coupling of a king with a divine mare which produced the divine twins. Some scholars, including Edgar Polomé, regard the reconstruciton of a PIE ritual as unjustified due to the difference between the attested traditions (EIEC s.v. Horse, p. 278).
The Brhadaranyaka Upanishad (a mystical appendix to the Shatapatha Brahmana and likely the oldest of the Upanishads) has a creation myth where "Death" takes the shape of a horse, and includes an identification of the Ashvamedha with the Sun:
The Upanishads describe ascetic austerities as an "inner Ashvamedha", as opposed to the "outer" royal ritual performed in the physical world, in keeping with the general tendency of Vedanta to move away from priestly ritual towards spiritual introspection; verse 6 of the Avadhuta Upanishad has:
Following Dayananda, Arya Samaj disputes the very existence of the pre-Vedantic ritual; thus Swami Satya Prakash Saraswati claims that
All World Gayatri Pariwar since 1991 has organized performances of a "modern version" of the Ashvamedha where a statue is used in place of a real horse, according to Hinduism Today with a million participants in Chitrakoot, Madhya Pradesh on April 16 to 20, 1994. Such modern performances are sattvika Yajnas where the animal is worshipped without killing it,, the religious motivation being prayer for overcoming enemies, the facilitation of child welfare and development, and clearance of debt, entirely within the allegorical interpretation of the ritual, and with no actual sacrifice of any animal, nor any sexual connotations.
The mock bestiality and necrophilia involved in the ritual caused considerable consternation among the scholars first editing the Yajurveda. Griffith (1899) omits verses VSM 23.20–31 (the ritual obscenities), protesting that they are "not reproducible even in the semi-obscurity of a learned European language" (alluding to other instances where he renders explicit scenes in Latin rather than English). A. B. Keith's 1914 translationalso omits verses.
This part of the ritual offended the Dalit reformer and framer of the Indian constitution B. R. Ambedkar and is frequently mentioned in his writings as an example of the perceived degradation of Brahmanical culture.