Verse 13.1.6.2

ādityānām patvānvihīti ādityānevainaṃ gamayati devā āśāpālā etaṃ devebhyo'śvam medhāya prokṣitaṃ rakṣateti śataṃ vai talpyā rājaputrā āśāpālāstebhya evainam paridadātīha rantiriha ramatāmiha dhṛtiriha svadhṛtiḥ svāheti saṃvatsaramāhutīrjuhoti ṣoḍaśa navatīretā vā aśvasya bandhanaṃ tābhirevainam badhnāti tasmādaśvaḥ pramukto bandhanamāgacati ṣoḍaśa navatīretā vā aśvasya bandhanaṃ tābhirevainam badhnāti tasmādaśvaḥ pramukto bandhanaṃ na jahāti

Preview of English translation:

2. “Go thou along the way of the Adityas!”—to the Adityas 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.

For a detailled translation, including proper diacritics and footnotes, go the full English translation.