Verse 4.3

प्राणाग्रय एवैतस्मिन्पुरे जाग्रति । गार्हपत्यो ह वा एषो३पानो व्यानोऽन्वाहार्यपचनो यद्गार्हपत्यात्प्रणीयते प्रणयनादाहवनीयः प्राणः ॥ ३ ॥

prāṇāgraya evaitasminpure jāgrati | gārhapatyo ha vā eṣo'pāno vyāno'nvāhāryapacano yadgārhapatyātpraṇīyate praṇayanādāhavanīyaḥ prāṇaḥ || 3 ||

3. The fires of prana alone wake in this city. This apana is the garhapatya fire. Vyana is the anvaharyopachana fire. The prana is the ahavaniya- fire, as it is taken from the garhapatya fire.

Shankara’s Commentary:

Com.—When the senses, the ear and the rest, are gone to sleep in this city, i.e., in this body of nine apertures, the five winds, prana and the rest, called fires, being like fire, keep watch. This is their similitude with fires. This apana is the garhapatya fire. How is explained; just as, at the time of performing the agnihotra, another fire named ahavaniya is obtained from the garhapatya, so from the apana during sleep, prana, as it were, the ahavaniya fire is obtained. But Vyana, emerging from the southern cavity of the heart is called the anvaharyapachana, or the southern fire, from its connection with the south.