Matsya Purana — Dialogue of Aṣṭaka and Yayāti: Exhaustion of Merit
शरीरदेहादिसमुच्छ्रयं च चक्षुःश्रोत्रे लभते केन संज्ञाम् एतत्सर्वं तात आचक्ष्व पृष्टः क्षेत्रज्ञं त्वां मन्यमाना हि सर्वे //
śarīradehādisamucchrayaṃ ca cakṣuḥśrotre labhate kena saṃjñām etatsarvaṃ tāta ācakṣva pṛṣṭaḥ kṣetrajñaṃ tvāṃ manyamānā hi sarve //
O dear one, by whom does this aggregate—body, embodied condition, and the rest—together with the eye and the ear, obtain awareness and recognition? Thus questioned, explain all this, for indeed everyone regards you as the Knower of the Field (kṣetrajña).
Indirectly, it points to an enduring conscious principle (kṣetrajña) distinct from the perishable body-sense aggregate—an idea often used in Purāṇic contexts to explain what remains unaffected through cosmic change, including pralaya.
By distinguishing the knower from the body and senses, it supports disciplined conduct: a king or householder should govern desires and sensory impulses, acting from discernment rather than mere bodily identification.
No direct Vāstu or ritual rule is stated; the verse is primarily metaphysical, framing the body and senses as ‘instruments’ whose true animator is the kṣetrajña—an idea sometimes invoked in ritual theory to emphasize inner awareness over mere external performance.