Matsya Purana — The Maheshvara Vow: Śiva-Caturdaśī Vrata
धर्मो ऽयं वृषरूपेण नन्दी नाम गणाधिपः धर्मान्माहेश्वरान् वक्ष्यत् यतःप्रभृति नारद //
dharmo 'yaṃ vṛṣarūpeṇa nandī nāma gaṇādhipaḥ dharmānmāheśvarān vakṣyat yataḥprabhṛti nārada //
This very Dharma, taking the form of a bull, is Nandī, the lord of Śiva’s attendants. From this point onward, O Nārada, he will expound the Maheśvara-dharmas—the duties and observances pertaining to Lord Maheśvara.
This verse does not discuss Pralaya; it marks a doctrinal transition into Maheśvara-dharma, identifying Nandī (bull-form) with Dharma as the authority for Śaiva observances.
By announcing Maheśvara-dharmas, it frames a set of righteous observances (vows, worship, conduct) that householders—and rulers as exemplars—may adopt to align governance and daily life with Dharma under Śiva’s tradition.
Architectural rules are not stated here; the ritual significance is the authorization of Śaiva practice: Nandī, as Dharma embodied, becomes the teacher who will prescribe Maheśvara-oriented rites and disciplines.