Matsya Purana — Agastya’s Origin
अस्य योजनमात्रे ऽपि जीवकोटिशतानि च निवसन्ति सुरश्रेष्ठ स कथं नाशमर्हति //
asya yojanamātre 'pi jīvakoṭiśatāni ca nivasanti suraśreṣṭha sa kathaṃ nāśamarhati //
O best of the gods, even within a space of only one yojana, hundreds of crores of living beings dwell; how, then, could it deserve destruction?
It frames Pralaya (or any destruction) as morally weighty by emphasizing the immense density of life even in a small space, implying that dissolution is not to be treated lightly and must align with cosmic justice.
It supports dharmic governance and household ethics centered on protection and non-harm: rulers and householders should consider the welfare of countless beings affected by their actions, avoiding needless destruction.
No direct Vastu or ritual rule is stated; the takeaway is an ethical principle useful for site planning and ritual decision-making—avoid actions that cause widespread harm to living communities occupying a given space.