Matsya Purana — The Episode of Madhu and Kaiṭabha: Gunas
*ब्रह्मोवाच एक इत्युच्यते लोकैर् अविचिन्त्यः सहस्रदृक् तत्संयोगेन भवतोः कर्म नामावगच्छताम् //
*brahmovāca eka ityucyate lokair avicintyaḥ sahasradṛk tatsaṃyogena bhavatoḥ karma nāmāvagacchatām //
Brahmā said: He is called by people “the One”—the unthinkable, the thousand-eyed. By communion with Him, may you both come to understand action (karma) and its true designation (its real nature and name).
Indirectly, it frames the supreme principle as “the One,” inconceivable and all-seeing—an idea often used in the Matsya Purana to ground cosmic processes (including creation and dissolution) in a single transcendent reality.
It emphasizes right understanding of karma—action and its true nature—which supports dharma-based conduct: rulers and householders are urged to perform duties with knowledge of their proper meaning and higher orientation toward the supreme.
While not giving Vāstu rules directly, the verse uses technical ritual language (karma as prescribed act), implying that correct rites—and by extension temple/ritual procedures—depend on understanding the proper definition and intention of the act.