Matsya Purana — The Strategy to Defeat Tāraka: Pārvatī’s Birth
समाप्तनियमा देवी यदा चोमा भविष्यति तदा स्वमेव तद्रूपं शैलजा प्रतिपत्स्यते //
samāptaniyamā devī yadā comā bhaviṣyati tadā svameva tadrūpaṃ śailajā pratipatsyate //
When the Goddess has completed her prescribed vows, and when she becomes Umā, then the Mountain-born one (Śailajā) will, of her own accord, assume that very form.
This verse does not discuss pralaya; it focuses on the Goddess’s completion of vows (niyama) and her voluntary assumption of the form called Umā.
It highlights the Purāṇic principle that disciplined observances (vrata/niyama) culminate in spiritual fruition—an ethical model for householders and rulers alike: steady restraint and completion of vowed duties lead to auspicious results.
Ritually, it underscores niyama/vrata-completion as the prerequisite for attaining a desired sacred state; while not giving Vāstu rules directly, it supports the broader Matsya Purāṇa emphasis on correct observance before consecrations and devotional rites.