Matsya Purana — Manvantaras
दिव्यानां साधनात्साधुर् ब्रह्मचारी गुरोर्हितः कारणात्साधनाच्चैव गृहस्थः साधुरुच्यते //
divyānāṃ sādhanātsādhur brahmacārī gurorhitaḥ kāraṇātsādhanāccaiva gṛhasthaḥ sādhurucyate //
A brahmacārin is called a sādhu because he pursues the means to what is divine and acts for the welfare of his teacher. Likewise, a householder is said to be a sādhu because he upholds the proper causes and the practical means (of sustaining dharma).
This verse is not about pralaya; it defines who is considered a sādhu within social-spiritual life, focusing on disciplined practice and dharmic support rather than cosmic dissolution.
It frames the gṛhastha as ‘sādhu’ when he sustains dharma through correct causes (kāraṇa—right intention/order) and correct means (sādhana—resources, work, charity, rituals). This supports the wider Matsya Purana ethic that stable household life underwrites society and righteous governance.
No direct Vāstu or iconography rule appears here; the ritual implication is general—householders are praised when they properly maintain dharmic means such as yajña, dāna, and daily duties that sustain sacred order.