Śivasaṃhitā 2.8

Here the Śivasaṃhitā assigns to iḍā a specific and irreplaceable physiological role: the distribution of nourishing nectar throughout the subtle body. The channel is not merely a passive conduit but an active vehicle of sustenance, analogous to the celestial Gaṅgā in its capacity to purify and maintain whatever it touches. The repetition in the verse emphasizes this point with unusual insistence.

The comparison to Mandākinī — the heavenly Gaṅgā — carries significant cosmological weight. In Purāṇic literature, Mandākinī flows through the celestial realms before descending to earth; here, that same sacred river is internalized within the subtle body. Puṣṭi, meaning nourishment or prosperity, distinguishes this flow from the liberating fire of piṅgalā — iḍā sustains, while piṅgalā transforms.

This verse provides the doctrinal basis for understanding why left-nostril breathing is prescribed in cooling, restorative contexts. When the body is depleted, feverish, or overstimulated, activating iḍā through deliberate breath regulation draws on this reservoir of lunar nectar. The Śivasaṃhitā here roots what might seem like a technical prescription in a rich cosmological narrative.