Māndukya 1.12

प्रभवः सर्वभावानां सतामिति विनिश्चयः। सर्वं जनयति प्राणश्चेतोंऽशून् पुरुषः पृथक् ॥१२॥

prabhavaḥ sarvabhāvānāṃ satāmiti viniścayaḥ। sarvaṃ janayati prāṇaścetoṃ'śūn puruṣaḥ pṛthak ॥12॥

[प्रभवः (prabhavaḥ) - origin; सर्व (sarva) - all; भावानां (bhāvānāṃ) - of beings; सताम् (satām) - of the good; इति (iti) - thus; विनिश्चयः (viniścayaḥ) - certainty; सर्वं (sarvaṃ) - all; जनयति (janayati) - creates; प्राणः (prāṇaḥ) - life; चेतः (cetaḥ) - concious being; अंशून् (aṃśūn) - parts; पुरुषः (puruṣaḥ) - the supreme person; पृथक् (pṛthak) - separately;]

The origin of all beings is certainly in the 'sat' — the good, the reality. The Supreme person individually creates all aspects of life and conscious beings.

Bhāshya 1.12

Ancient testimonial is quoted with the same terminology, 'sat' (good, reality) and 'asat' (false, non-reality), attributing the supreme person to Lord Narayana.

"प्रभवः सर्वभावानां विष्णुरेव न संशयः। इत्थं सतां निश्चयः स्यादन्यथा त्वसतां भवेत्। सर्वस्य हि प्रणेतृत्वात् प्राणो नारायणः परः॥"

"prabhavaḥ sarvabhāvānāṃ viṣṇureva na saṃśayaḥ। itthaṃ satāṃ niścayaḥ syādanyathā tvasatāṃ bhavet। sarvasya hi praṇetṛtvāt prāṇo nārāyaṇaḥ paraḥ॥"

[प्रभवः (prabhavaḥ) - origin; सर्व (sarva) - all; भावानां (bhāvānāṃ) - beings; विष्णुः (viṣṇuḥ) - Vishnu; एव (eva) - indeed; न (na) - not; संशयः (saṃśayaḥ) - doubt; इत्थं (itthaṃ) - thus; सतां (satāṃ) - of the good; निश्चयः (niścayaḥ) - certainty; स्यात् (syāt) - is; अन्यथा (anyathā) - otherwise; तु (tu) - but; असतां (asatāṃ) - unreal, non-good; भवेत् (bhavet) - becomes; सर्वस्य (sarvasya) - of all; हि (hi) - indeed; प्रणेतृत्वात् (praṇetṛtvāt) - due to being the leader; प्राणः (prāṇaḥ) - of life-force; नारायणः (nārāyaṇaḥ) - is Narayana; परः (paraḥ) - the supreme;]

"Vishnu is undoubtedly the origin of all beings. Thus, there is the certainty of 'sat', i.e. good or reality; otherwise, it becomes unreal or bad. Indeed, due to being the leader of all life force, he is the supreme Lord Narayana."