Shatapatha Brahmana · Chapter 13.1.6

vibhūrmātrā prabhūḥ pitreti iyaṃ vai mātā'sau pitā''bhyāmevainaṃ paridadātyaśvo'si hayo'sīti śāstyevainaṃ tattasmācchiṣṭāḥ prajā jāyante'tyo'si mayo'sītyatyevainaṃ nayati tasmādaśvaḥ paśūnāṃ śraiṣṭhyaṃ gacchatyarvāsi saptirasi vājyasīti yathāyajurevaitadvṛṣāsi nṛmaṇā asīti mithunatvāya yayurnāmāsi śiśurnāmāsītyetadvā aśvasya priyaṃ nāmadheyaṃ priyeṇaivainaṃ nāmnābhivadati tasmādapyāmitrau saṃgatya nāmnā cedabhivadato'nyo'nyaṃ sameva jānāte -

ādityānāṃ patvānvihīti ādityānevainaṃ gamayati devā āśāpālā etaṃ devebhyo'śvam
medhāya prokṣitaṃ rakṣateti śataṃ vai talpyā rājaputrā āśāpālāstebhya evainamparidadātīha rantiriha ramatāmiha dhṛtiriha svadhṛtiḥ svāheti saṃvatsaramāhutīrjuhoti ṣoḍaśa navatīretā vā aśvasya bandhanaṃ tābhirevainambadhnāti tasmādaśvaḥ pramukto bandhanamāgacchati ṣoḍaśa navatīretā vā aśvasya bandhanaṃ tābhirevainaṃ badhnāti tasmādaśvaḥ pramukto bandhanaṃ na jahāti -

rāṣṭraṃ vā aśvamedhaḥ rāṣṭra ete vyāyacchante ye'śvaṃ rakṣanti teṣāṃ ya udṛcaṃ gacchanti rāṣṭreṇaiva te rāṣṭraṃ bhavantyatha ye nodṛcaṃ gacchanti rāṣṭrātte vyavacchidyante tasmādrāṣṭryaśvamedhena yajeta parā vā eṣa sicyate yo'balo'śvamedhena yajate yadyamitrā aśvaṃ vinderanyajño'sya vicchidyeta pāpīyāntsyācchataṃ kavacino rakṣanti yajñasya saṃtatyā avyavacchedāya na pāpīyānbhavatyathānyamānīya prokṣeyuḥ saiva tatra prāyaścittiḥ -