15.14 अहम् I, वैश्वानरः (the fire) Vaisvanara, भूत्वा having become, प्राणिनाम् of living beings, देहम् the body, आश्रितः abiding, प्राणापानसमायुक्तः associated with Prana and Apana, पचामि (I) digest, अन्नम् food, चतुर्विधम् fourfold.Commentary: The immanence of the Lord as the gastric fire in all living beings is described in this verse.Vaisvanara The fire that abides in the stomach. This fire is fanned by the bellows of the incoming and the outgoing breaths continuously and large antities of food are digested. Inside the wonderful laboratory of the stomach I digest the food by taking the form of this gastric fire.Four kinds of food (1) Food which has to be eaten by mastication (Bhakshyam). (2) That which has to be sucked in (Bhojyam). (3) That which has to be licked (Lehyam). (4) That which has to be devoured or swallowed (Choshyam). Another classification is as follows (1) Rice is PrithiviAnnam (solid food) for human beings. (2) Water is Apyannam (watery food) for birds like the Chataka. (3) Fire is Tejasannam (hot food) for certain creatures. (4) Air is Vayvannam (air as food) for serpents.अयमग्निर्वैश्वानरो योऽयमन्तः पुरुषः येनेदमन्नं पच्यते।।This fire which is within man and by which the food is digested is Vaisvanara. (Brihadaranyaka Upanishad 5.9.1)He who thinks or meditates and feels that the Vaisvanara fire is the eater, that the food eaten by the fire is the Soma (moon) and that the two together form AgniSoma is not contaminated by the impurities in the food. He who meditates before he takes his food that the whole world which is in the form of eater and eaten is made up of Agni and Soma, is not tainted by the evil arising from eating bad food.Repeat this verse daily before you take your food. You will be free from all taints of impurity in food.