Sadācāra–Varṇa-lakṣaṇa and Prātaḥkṛtya
Right Conduct, Social Typologies, and Morning Purification
आपोहिष्ठेति शिरसि प्रोक्षयेत्पापशांतये । यस्येति मंत्रं पादे तु संधिप्रोक्षणमुच्यते
āpohiṣṭheti śirasi prokṣayetpāpaśāṃtaye | yasyeti maṃtraṃ pāde tu saṃdhiprokṣaṇamucyate
For the pacification of sin, one should sprinkle purifying water upon the head while reciting the mantra beginning with “Āpo hi ṣṭhā…”. And the mantra beginning with “Yasya…” is to be applied at the feet—this is called the sprinkling at the joints (limbs) as part of the rite.
Suta Goswami
Tattva Level: pasha
Shiva Form: Mahādeva
It teaches that inner and outer purity support Shiva-upāsanā: sprinkling sanctified water with Vedic mantras is prescribed to calm the effects of pāpa and make the practitioner fit for devotion to Pati (Shiva).
Before approaching Saguna Shiva in the form of the Linga, the worshipper performs ritual śuddhi (purification). Prokṣaṇa prepares the body and senses so the subsequent linga-pūjā, abhiṣeka, and mantra-japa are done in a consecrated state.
Perform prokṣaṇa (sprinkling) with clean water: recite “Āpo hi ṣṭhā…” while sprinkling the head, and recite “Yasya…” while sprinkling the feet (as limb/joint purification) before continuing Shiva pūjā.