Adhyaya 89: शौचाचारलक्षणम् — सदाचार, भैक्ष्यचर्या, प्रायश्चित्त, द्रव्यशुद्धि, आशौच-निर्णय
तस्मात्सर्वप्रयत्नेन न संभाष्या रजस्वला प्रथमे ऽहनि चाण्डाली यथा वर्ज्या तथाङ्गना
tasmātsarvaprayatnena na saṃbhāṣyā rajasvalā prathame 'hani cāṇḍālī yathā varjyā tathāṅganā
तस्मात् सर्वप्रयत्नेन प्रथमेऽहनि रजस्वलां न संभाषेत्। तदा सा चाण्डालीव वर्ज्या; तथैव ताम् अङ्गनां पृथक् स्थापयेत्।
Suta Goswami (narrating Linga Purana teachings to the sages of Naimisharanya)
It frames shaucha (ritual discipline) as a preparatory boundary for approaching Shiva-linga worship, emphasizing temporary separation on the first day as part of maintaining ritual readiness.
Indirectly, it presents Shiva as Pati—the supremely pure Lord—whose worship is approached through regulated conduct; the pashu (individual) reduces pasha (impurities/constraints) by observances that cultivate fitness for puja.
A shaucha-based restriction: on the first day of menstruation, one avoids close interaction as part of maintaining ritual purity norms connected to Shiva-puja discipline.