Śatapatha Brāhmaṇa ("of a hundred paths") 13.1.2

Now, unsuccessful in the sacrifice, assuredly, is what is performed without a formula. (With Vâg. S. XXII, 2,) 'This rope did they take, at the first age of the truth, [the sages, at the rites: it hath been with us at this Soma-sacrifice, declaring the course in the gaining of the truth],' he takes the halter of the horse in order to supply a formula for the success of the sacrifice. It (the rope) is twelve cubits long,--twelve months make a year: it is the year, the sacrifice, he secures.

Concerning this they say, 'Is the rope to be made twelve cubits long, or thirteen cubits long?' Well, that year is the bull among the seasons, and the thirteenth (or intercalary) month is an excrescence of the year; and this Asvamedha is the bull among sacrifices; and inasmuch as the bull has an excrescence (hump), one may add on a thirteenth cubit to the rope as an excrescence to this (Asvamedha): even as the bull's hump is attached (to his back), suchlike would this be.

[He puts the halter on the horse, with Vâg. S. XXII, 3, 4,] 'Encompassing thou art,'-- therefore the offerer of the Asvamedha conquers all the quarters;--'the world thou art,'--the world he thus conquers;--'a ruler thou art, an upholder,'--he thus makes him a ruler and upholder;--'go thou unto Agni Vaisvânara,'--he thus makes him go to Agni Vaisvânara (the friend of all men);--'of wide extent,'--he thus causes him to extend in offspring and cattle;--'consecrated by Svâhâ (hail!),'--this is the Vashat-call for it;--'good speed (to) thee for the gods!'--he thus makes it of good speed for the gods;--'for Pragâpati,'--the horse is sacred to Pragâpati: he thus supplies it with his own deity.

But, verily, he who fetters the horse without announcing it to the Brahman and the gods is liable to incur injury. He addresses the Brahman (the superintending priest) by saying, 'O Brahman, I will fetter the horse for the gods, for Pragâpati: may I prosper therewith!' and having made the announcement to the Brahman, he ties up the horse, and thus incurs no injury. 'Fetter it for the gods, for Pragâpati: prosper thou therewith!' thus the Brahman urges him, and supplies it (the horse) with its own deity. He then sprinkles it (with water): the (symbolic) meaning of this is the same as before.

He sprinkles it, with (Vâg. S. XXII, 5), 'I sprinkle thee (so as to be) acceptable to Pragâpati,'--for Pragâpati is the most vigorous of the gods: it is vigour he bestows on it, whence the horse is the most vigorous of animals.

'I sprinkle thee, acceptable to Indra and Agni,'--for Indra and Agni are the most powerful of the gods: it is power he bestows on it, whence the horse is the most powerful of animals.

'I sprinkle thee, acceptable to Vâyu,'--for Vâyu is the swiftest of gods: it is speed he bestows on it, whence the horse is the swiftest of animals.

'I sprinkle thee, acceptable to the All-gods,'--for the All-gods are the most famous of gods: it is fame he bestows on it, whence the horse is the most famous of animals,---'I sprinkle thee, acceptable to all the gods.'

Concerning this they say, 'Seeing that the horse is sacred to Pragâpati, wherefore (does he say), "I sprinkle thee" for other deities also?' Well, all the gods are concerned in the horse-sacrifice; when he says, 'I sprinkle thee for all the gods,' he makes all the gods take a concern in the horse-sacrifice; whence all the gods are concerned in the horse-sacrifice. But his wicked enemy seeks to lay hold of him who performs the horse-sacrifice, and the horse is a thunderbolt;--having killed the four-eyed dog, he--with 'Undone is the man! undone is the dog!'--plunges it under the horse's feet: it is by means of the thunderbolt he thus stamps him down; and the wicked enemy does not lay hold of him.