Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
यस्मात्प्रविष्टास्ते ऽन्योन्यं तस्मात्ते स्थिरतां गताः आसंस्ते ह्यविशेषाश्च विशेषा अन्यवेशनात् //
yasmātpraviṣṭāste 'nyonyaṃ tasmātte sthiratāṃ gatāḥ āsaṃste hyaviśeṣāśca viśeṣā anyaveśanāt //
Because they entered into one another, therefore they attained stability. Indeed, at first they were without distinction; differentiation arose due to their mutual interpenetration.
It explains a key sarga principle: the elements become stable and form the manifest world when they mutually enter and combine; prior to such combination they remain undifferentiated—an idea that also helps describe how manifestation withdraws back toward indistinction in pralaya.
By analogy, it supports the Matsya Purana’s ethical emphasis on social stability: order and ‘sthiratā’ in a kingdom or household arises through proper integration of complementary roles and qualities rather than remaining in an unstructured, indistinct state.
Though not a direct Vāstu rule, the principle underlies Vāstu reasoning: stable forms arise from correct composition and proportion of elemental qualities (bhūta-samyoga), a conceptual basis often invoked when explaining why balanced material combinations and orientations produce durable, harmonious structures.