Śatapatha Brāhmaṇa ("of a hundred paths") 13.1.6

[The Adhvaryu and Sacrificer whisper in the right ear of the horse, Vâg. S. XXII, 19,] 'Plenteous by the mother, strengthful by the father,'--its mother, doubtless, is this (earth), and its father yonder (sky): it is to these two he commits it;--'a horse thou art, a steed thou art,'--he thereby instructs it, whence clever subjects (or children) are born to him;--'a courser (atya) thou art, a charger thou art,'--he therewith leads it beyond (ati), whence the horse goes beyond (surpasses) other animals, and whence the horse attains to pre-eminence among animals;--'a runner thou art, a racer thou art, a prize-winner thou art,'--in accordance with the text is (the meaning of) this;--'a male thou art, well-disposed towards man thou art,'--this is with a view to its (or, his) being supplied with a mate;--'Speedy thou art called, Child thou art called,'--this is the horse's favourite name: by its favourite name he thus addresses it; whence even if two enemies, on meeting together, address one another by name, they get on amicably together.

'Go thou along the way of the Âdityas!'--to the Âdityas he thus makes it go.--'Ye divine guardians of the quarters, protect this horse, sprinkled for sacrifice to the gods!'--the guardians of the quarters are a hundred princes born in wedlock: to them he commits it;--'here is joy: here let it rejoice!--here is safe keeping, here is its own safe keeping, hail!' For a year he offers the (four Dhriti) oblations --(amounting to) sixteen nineties, for they are the horse's chain, and it is therewith alone that he chains it; whence the horse when let loose returns to its chain: (they amount to) sixteen nineties; for these (oblations of safe keeping) are the horse's chain, and it is therewith alone that he chains it, whence the horse, when let loose, does not (entirely) abandon its chain.

Verily, the Asvamedha means royal sway: it is after royal sway that these strive who guard the horse. Those of them who reach the end become (sharers in) the royal sway, but those who do not reach the end are cut off from royal sway. Wherefore let him who holds royal sway perform the horse-sacrifice; for, verily, whosoever performs the horse-sacrifice, without possessing power, is poured (swept) away.--Now, were unfriendly, men to get hold of the horse, his sacrifice would be cut in twain, and he would become the poorer for it. A hundred men clad in armour guard it for the continuity and uninterrupted performance of the sacrifice; and he will not become the poorer for it; (but if it be lost) they should fetch another (horse), and sprinkle it: this is the expiation in that case.