अथ योऽस्य प्रत्यङ्सुषिः सोऽपानः सा वाक्सोऽग्निस्तदेतद्ब्रह्मवर्चसमन्नाद्यमित्युपासीत ब्रह्मवर्चस्यन्नादो भवति य एवं वेद ॥ ३.१३.३ ॥
In plain words
Its western opening is the down-breath, and that is speech, and that is fire. Let a man worship it as the lustre of Brahman and food. He who knows this becomes lustrous with Brahman and an eater of food.