Matsya Purana — Manvantaras
वृद्धाश्चालोलुपाश्चैव आत्मवन्तो ह्यदाम्भिकाः सम्यग्विनीता मृदवस् तानाचार्यान्प्रचक्षते //
vṛddhāścālolupāścaiva ātmavanto hyadāmbhikāḥ samyagvinītā mṛdavas tānācāryānpracakṣate //
Those who are mature in years, free from greed, self-possessed and without pretence, well-disciplined and gentle—such persons are recognized and spoken of as true teachers (ācāryas).
This verse is not about pralaya; it defines the moral qualifications of an ācārya—greedlessness, humility, discipline, and gentleness.
It guides rulers and householders in choosing worthy teachers and advisors: those who are self-controlled, non-pretentious, and properly disciplined, rather than merely eloquent or powerful.
No vastu or temple-building rule is stated; the ritual takeaway is that instruction and rites should be learned from qualified, humble, disciplined ācāryas.