Śatapatha Brāhmaṇa ("of a hundred paths") 13.5.3.10

13.5.3.10

ekaviṃśatiḥ savanīyāḥ paśavaḥ sarva āgneyāsteṣāṃ samānaṃkarmetyu haika āhuścaturviṃśatim tvevaitāngavyānālabhet dvādaśabhyo devatābhyo dvādaśa māsāḥ samvatsaraḥ sarvaṃ samvatsaraḥ sarvamaśvamedhaḥ sarvasyāptai sarvasyāvaruddhyai

Its Bahishpavamâna (stotra) is in the Trivrit (9-versed Stoma), the Âgya (stotras) in the Pañkadasa (15-versed), the Mâdhyandina-pavamâna in the Saptadasa (17), the Prishthas in the Ekavimsa (21), the Tritîya Pavamâna in the Trinava (27), the Agnishtoma-sâman in the Trayastrimsa (33), the Ukthas in the Ekavimsa (21), the Shodasin in the Ekavimsa, the night (chants) in the Pañkadasa, the Sandhi (twilight chant) in the Trivrit (9). Whatever Sastra is (recited) for the second day of the Prishthya Shadaha that is (used at) the Atirâtra sacrifice; thereby he causes yonder (heavenly) world to prosper.