Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.1.31

4.2.1.31

atha hotrāṇāṃ camasānabhyunnayanti | hutociṣṭā vā ete saṃsravā bhavanti nālamāhutyai tānevaitatpunarāpyāyayanti tathālamāhutyai bhavanti tasmāddhotrāṇāṃ camasānabhyunnayanti

They now fill up the cups of the fire-priests. For those residues are remains of oblations, insufficient for offering: he now fills them up again, and thus they become sufficient for offering: therefore they fill up the cups of the fire-priests.