Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.3.12

4.2.3.12

mitrāvaruṇābhyāṃ tvā | devāvyaṃ yajñasyāyuṣe gṛhṇāmītyeva maitrāvaruṇāya maitrāvaruṇīṣu hi tasmai stuvate maitrāvaruṇīranuśaṃsati maitrāvaruṇyā yajati

With, 'Thee, the god-pleasing, I take for Mitra and Varuna, for the life of the sacrifice!' (he takes the portion) for the Maitrâvaruna priest;--for in verses to Mitra and Varuna they (the Udgâtris) chant praises for this (libation); and he (the Hotri) afterwards recites verses to Mitra and Varuna for the sastra, and offers with a verse to Mitra and Varuna.