Matsya Purana — Manvantaras
क्षत्रियाणां वरा ह्येते विज्ञेया मन्त्रवादिनः भलन्दकश्च वासाश्वः संकीलश्चैव ते त्रयः //
kṣatriyāṇāṃ varā hyete vijñeyā mantravādinaḥ bhalandakaśca vāsāśvaḥ saṃkīlaścaiva te trayaḥ //
These are to be known as the foremost among the Kshatriyas, skilled as mantravādins in the recitation and utterance of mantras: Bhalandaka, Vāsāśva, and Saṃkīla—these three indeed.
Nothing directly—this verse is not about Pralaya; it is a genealogical-style enumeration praising three Kshatriyas as mantra-knowers.
It highlights an ideal of Kshatriya excellence: beyond warfare and governance, exemplary rulers were also expected to be trained in mantra-knowledge and sacred recitation, linking kingship with Vedic discipline.
No Vastu/architecture rule is stated; the ritual implication is the esteem given to 'mantravādins'—those competent in mantras—indicating the ritual literacy valued among elite Kshatriyas.