Śatapatha Brāhmaṇa ("of a hundred paths") 8.4.4.7

8.4.4.7

annaṃ saptadaśavatyau | te yatsaptadaśavatyau bhavataḥ saptadaśaṃ hyannaṃ dve bhavato dvyakṣaraṃ hyannaṃ te anantarhite pañcadaśavatībhyāmupadadhātyanantarhitaṃ tadbāhubhyāmannaṃ dadhāti bāhye pañcadaśavatyau bhavato 'ntare saptadaśavatyau bāhubhyāṃ tadubhayato 'nnam parigṛhṇāti

The two containing the Saptadasa are food. And as to why they are such as contain the Saptadasa,--food is seventeenfold. There are two of them, because 'anna' (food) has two syllables. He lays them down close to those containing the Pañkadasa he thus puts the food close to the arms. Those containing the Pañkadasa are on the outside, and those containing the Saptadasa on the inside: he thus encloses the food on both sides by the arms.