Matsya Purana — Kṛṣṇāṣṭamī Vrata: Monthly Śiva-Names
स्थाणुं चैत्रे शिवं तद्वद् वैशाखे त्वर्चयेन्नरः ज्येष्ठे पशुपतिं चार्चेद् आषाढे उग्रमर्चयेत् //
sthāṇuṃ caitre śivaṃ tadvad vaiśākhe tvarcayennaraḥ jyeṣṭhe paśupatiṃ cārced āṣāḍhe ugramarcayet //
In the month of Caitra, a man should worship Śiva as Sthāṇu; likewise in Vaiśākha he should worship him as Śiva. In Jyeṣṭha he should worship Paśupati, and in Āṣāḍha he should worship him as Ugra.
This verse is not about pralaya; it prescribes a ritual calendar—worshipping Śiva under specific epithets in specific lunar months.
It frames monthly devotional discipline (vrata/anuṣṭhāna) as a dharmic duty: the worshipper maintains regular observance by honoring Śiva through appropriate names aligned with the ritual calendar.
Ritually, it teaches nāma-upāsanā (worship by epithets) and month-wise scheduling of pūjā; it implies selecting the deity’s invoked form/name (Sthāṇu, Śiva, Paśupati, Ugra) according to the month.