Matsya Purana — The Greatness and Procedure of the Sarva-Phala-Tyaga Vrata
यथा भेदं न पश्यामि शिवविष्ण्वर्कपद्मजान् तथा ममास्तु विश्वात्मा शंकरः शंकरः सदा //
yathā bhedaṃ na paśyāmi śivaviṣṇvarkapadmajān tathā mamāstu viśvātmā śaṃkaraḥ śaṃkaraḥ sadā //
As I perceive no difference between Śiva, Viṣṇu, the Sun, and the Lotus-born (Brahmā), so may Śaṅkara—who is the very Soul of the universe—ever be mine, ever be my refuge.
It does not describe Pralaya directly; it establishes a theological principle that the cosmic functions associated with Brahmā (creation), Sūrya (cosmic order/time), Viṣṇu (preservation), and Śiva (transformation) are ultimately non-different in essence.
By teaching non-sectarian reverence and seeing unity among deities, it supports dharmic conduct—reducing religious rivalry, encouraging tolerance, and grounding daily worship (nitya-karma) in a single, harmonized vision of the Divine.
No Vāstu or temple-measurement rule is stated; ritually, the takeaway is ekatva-bhāva—one may worship Śaṅkara with the understanding that the same Supreme is honored through Śiva, Viṣṇu, Sūrya, and Brahmā.