Matsya Purana — Solar–Lunar Motions
भूतारम्भकृतं कर्म आशिषश्च विशां पते प्रारभन्ते लोककामास् तेषां पन्थाः स दक्षिणः //
bhūtārambhakṛtaṃ karma āśiṣaśca viśāṃ pate prārabhante lokakāmās teṣāṃ panthāḥ sa dakṣiṇaḥ //
O lord of the people, actions undertaken with involvement in worldly beings and the pursuit of blessings (āśīṣ) set worldly desires in motion; the course they follow is the southern path.
It does not describe Pralaya directly; it explains karmic causation—how worldly, desire-driven actions generate continuing trajectories (the ‘southern path’) rather than liberation.
It cautions that actions pursued for boons and worldly outcomes fuel lokakāma (worldly desire). A king/householder should govern and act with dharma, knowing that desire-driven rites and rewards bind one to cyclical results.
No Vāstu rule is stated, but the verse reflects ritual logic: actions and ‘āśiṣ’ (sought blessings/boons) propel karmic results—useful when interpreting why certain rites are prescribed for worldly aims rather than mokṣa.