Śatapatha Brāhmaṇa ("of a hundred paths") 13.5.1.9

13.5.1.9

athāto mādhyandinaṃ savanaṃ aticandāḥ pratipanmarutvatīyasya trikadrukeṣu mahiṣo yavāśiramityatiṣṭhā vā eṣā candasāṃ yadaticandā atiṣṭhā aśvamedho yajñānāmaśvamedhasyaivāptyai saiṣaiva triḥ śastā tricaḥ sampadyate teno taṃ kāmamāpnoti yastrica idaṃ vaso sutamandha ityanucara eṣa eva nitya ekāhātāna itthā hi soma inmade'vitāsi sunvato vṛktabarhiṣa iti paṅktīśca ṣaṭpadāśca śastvaikāhike nividaṃ dadhātīti marutvatīyam

Then as to the midday-service. For the obtainment of the Asvamedha, the atikhandas (verse, II, 22, 1), 'In the three troughs the buffalo drank the barley-draught,' is the opening verse of the Marutvatîya (sastra); for outstanding, indeed, is this atikhandas (hypercatalectic verse) amongst metres, and outstanding is the Asvamedha amongst sacrifices. This (verse), being recited thrice, amounts to a triplet, and thereby he obtains the object of desire which (may be contained) in the triplet. 'Here, O good one, is the pressed plant' (Rig-veda VIII, 2, 1-3) is the 'anukara' (sequent triplet): this same (triplet) is the constant connecting link of the one-day's sacrifice. Having recited both the paṅkti (verses, I, 80, 1-16) 'Here in the Soma-draught alone (the Brahman gave thee strength),' and the six-footed ones (VIII, 36, 1-7) 'The patron thou art of the offerer of Soma,' he inserts the Nivid in the (hymn) of the one-day's sacrifice. Thus as to the Marutvatîya (-sastra).