Śatapatha Brāhmaṇa ("of a hundred paths") 13.5.4.9

13.5.4.9

trivṛdagniṣṭomaḥ pañcadaśa ukthyaḥ saptadaśaṃ tṛtīyamahaḥ sokthakamekaviṃśaḥ ṣoḍaśī pañc=daśī rātristrivṛtsandhirityeṣo'nuṣṭupsampannastena haitena dhvasā dvaitavanaīje mātsyo rājā yatraitaddvaitavanaṃ sarastadetadgāthayābhigītaṃ caturdaśa dvaitavano rājā saṅgrāmajiddhayān indrāya vṛtraghne'badhnāttasmāddvaitavanaṃ sara iti

The Agnishtoma in the Trivrit (stoma); the Ukthya in the Pañkadasa; and the third day, with the Uktha (stotras), in the Saptadasa; the Shodasin (stotra) in the Ekavimsa, the night (stotras) in the Pañkadasa, and the Sandhi (stotra) in the Trivrit,--this is the (sacrifice) resulting in the Anushtubh: it is therewith that sacrifice was performed by Dhvasan Dvaitavana, the king of the Matsyas, where there is the lake Dvaitavana; and it is of this that the Gâthâ sings,--'Fourteen steeds did king Dvaitavana, victorious in battle, bind for Indra Vritrahan, whence the lake Dvaitavana (took its name).'