Matsya Purana — The Dialogue of Kacha and Devayani: Dharma
फलिष्यति न मे विद्या त्वद्वचश्चेति तत्तया अध्यापयिष्यामि च यं तस्य विद्या फलिष्यति //
phaliṣyati na me vidyā tvadvacaśceti tattayā adhyāpayiṣyāmi ca yaṃ tasya vidyā phaliṣyati //
“My learning will not bear fruit—such is your word.” Therefore, with that resolve, I shall teach the one whom you indicate; his knowledge will indeed bear fruit.
This verse does not describe Pralaya directly; it emphasizes that knowledge becomes effective (phala-yukta) when taught in accordance with divine instruction—an ethical principle that can operate even in Pralaya-related narratives.
It frames a key duty: to obey righteous counsel and ensure knowledge is transmitted to a proper recipient. For a king (like Manu), governance includes preserving and propagating dharma-knowledge through qualified instruction.
No explicit Vastu or ritual procedure is stated; however, the verse supports the broader Matsya Purana principle that technical sciences (including Vastuvidya) yield results only when taught and applied under correct authority and method.