Matsya Purana — Genealogy from Budha to Purūravas and Yayāti; Raji’s war episode; the Paurava...
रजिराराधयामास नारायणमकल्मषम् तपसा तोषितो विष्णुर् वरान्प्रादान्महीपते //
rajirārādhayāmāsa nārāyaṇamakalmaṣam tapasā toṣito viṣṇur varānprādānmahīpate //
King Rajira worshipped Nārāyaṇa, the stainless Lord. Pleased by his austerities (tapas), Viṣṇu granted him boons, O lord of the earth.
This verse does not discuss pralaya; it highlights devotional austerity (tapas) as a means to please Vishnu and obtain divine favor.
It presents an ideal royal model: a king should uphold dharma through disciplined worship and tapas, seeking divine guidance rather than mere conquest or pleasure.
No specific vastu or temple-building rule is stated; the ritual takeaway is that sincere worship and austerity are portrayed as efficacious means of propitiating Nārāyaṇa.