Bhagwad Gita
Chapter 15, Verse 14
अहं वैश्वानरो भूत्वा प्राणिनां देहमाश्रितः।प्राणापानसमायुक्तः पचाम्यन्नं चतुर्विधम्।।15.14।।
I am the fire of digestion in every living body, and I am the air of life, outgoing and incoming, by which I digest the four kinds of foodstuff.