Adhyaya 89: शौचाचारलक्षणम् — सदाचार, भैक्ष्यचर्या, प्रायश्चित्त, द्रव्यशुद्धि, आशौच-निर्णय
ईक्षयेद्भास्करं देवं ब्रह्मकूर्चं ततः पिबेत् केवलं पञ्चगव्यं वा क्षीरं वा चात्मशुद्धये
īkṣayedbhāskaraṃ devaṃ brahmakūrcaṃ tataḥ pibet kevalaṃ pañcagavyaṃ vā kṣīraṃ vā cātmaśuddhaye
ให้เพ่งดูพระภาสกร ผู้เป็นสุริยะอันศักดิ์สิทธิ์ แล้วจึงดื่มพรหมกูรจะ หรือเพื่อความชำระภายใน จะรับเพียงปัญจคัวยะเท่านั้น หรือดื่มนมเท่านั้นก็ได้
Suta Goswami (narrating Śaiva purification rites to the sages of Naimiṣāraṇya)
It prescribes ātma-śuddhi (inner purification) as a prerequisite for Śiva-liṅga worship—using auspicious darśana of Sūrya and purifying intake (brahma-kūrca/pañcagavya/milk) so the practitioner becomes ritually and mentally fit for Śaiva upāsanā.
Indirectly: it implies that approaching Pati (Śiva) requires the paśu to lessen mala and bondage through purification; Śiva-tattva is the supremely pure reality, and the seeker aligns with that purity through preparatory disciplines.
A preparatory śauca-prayoga: Sūrya-darśana followed by drinking a purificatory substance (brahma-kūrca, or pañcagavya, or milk) as an expiatory and sattva-enhancing rite before Śaiva observances.