Matsya Purana — Kṛṣṇāṣṭamī Vrata: Monthly Śiva-Names
पूजयेच्छ्रावणे शर्वं नभस्ये त्र्यम्बकं तथा हरमाश्वयुजे मासि तथेशानं च कार्त्तिके //
pūjayecchrāvaṇe śarvaṃ nabhasye tryambakaṃ tathā haramāśvayuje māsi tatheśānaṃ ca kārttike //
In the month of Śrāvaṇa one should worship Śarva; in Bhādrapada, likewise, Tryambaka; in Āśvayuja one should worship Hara; and in Kārttika, Īśāna as well.
This verse is not about pralaya; it prescribes a ritual calendar—assigning specific names/forms of Śiva to be worshipped in particular lunar months.
It frames dharmic routine through month-wise pūjā: a king or householder maintains religious merit and social order by observing regular worship aligned with the sacred calendar.
Ritually, it establishes a structured upāsanā sequence—worshipping Śiva under distinct epithets across months—useful for planning temple liturgy and monthly pūjā schedules (though no specific Vāstu rule is stated).