Having inhaled through the solar channel, filling the abdomen slowly, practicing kumbhaka according to the rules, one should exhale again through the lunar channel.

This verse completes the nāḍī śodhana cycle begun in the previous verse. Now inhalation is through sūrya (piṅgalā/right) and exhalation through candra (iḍā/left). A complete cycle includes both directions.

The instruction śanaiḥ means “slowly” or “gradually.” Inhalation should not be abrupt but smooth, allowing the abdomen (udara) to fill completely. This indicates deep diaphragmatic breathing.

Vidhivat means “according to the prescribed rules” or “in the correct manner.” This refers to the specific proportions and techniques the guru teaches, including the use of bandhas during kumbhaka and ratios appropriate for the practitioner’s level.

Together, verses 17 and 18 describe the practice that later texts call anuloma-viloma or nāḍī śodhana. This technique is considered the most important of the preparatory practices, and many teachers prescribe it for months or years before introducing more intense kumbhakas.