Śatapatha Brāhmaṇa ("of a hundred paths") 9.2.3.48

9.2.3.48

tadyā amūstisro 'nuṣṭubhaḥ | gārhapatye sampādayanti tāsāmetāmatrikāmāharanti tadyadetāmatrāharantyatraiṣa sarvo 'gniḥ saṃskṛtaḥ sa eṣo 'tra tasmai nālamāsīdyadannamātsyat

And this one (Anushtubh) they bring hither from those three Anushtubhs which they make up on the Gârhapatya; and inasmuch as they bring this (therefrom) hither, thereby this whole Agni (fire-altar) becomes completed. But now he was not yet fit to eat food.