In the Skandapurana we have an Advaitic expression of Brahman and a rephrasing of the Shvetashvatara Upanishad:
~ स्कन्दपुराणम्/खण्डः ३ (ब्रह्मखण्डः)/ब्रह्मोत्तर खण्डः/अध्यायः २१
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सर्गात्पुरा निरालोकं यदेकं निष्कलं परम् ।।
चिदानंदमयं ज्योतिः स आद्यः केवलः शिवः ।। १२ ।।
Before creation Brahman, the partless, Pure Consciousness, Bliss, Resplendent, the First, One only, Shiva the Supreme remained.
स एवादौ रजोरूपं सृष्ट्वा ब्रह्माणमात्मना ।।
सृष्टिकर्मनियुक्ताय तस्मै वेदांश्च दत्तवान् ।। १३ ।।
He alone, at the beginning, after creating the Rajo-formed Brahmaa, from Himself, assigning the function of creating the world to him. He also blessed him with the Vedas.
The above is sourced from the Shvetashvataropanishad:
‘यो ब्रह्माणं विदधाति पूर्वं यो वै वेदांश्च प्रहिणोति तस्मै । तꣳ ह देवमात्मबुद्धिप्रकाशं मुमुक्षुर्वै शरणमहं प्रपद्ये’ (श्वे. उ. ६ । १८)
I, a Vedantic aspirant, take refuge in that Rudra who in the yore created Brahma and blessed him with the Veda.
पुनश्च दत्तवानीश आत्मतत्त्वैकसंग्रहम् ।।
सर्वोपनिषदां सारं रुद्राध्यायं[१] च दत्तवान् ।। १४ ।।
Shiva gave Brahmaa the concise Self knowledge that is the essence of the Upanishadic corpus which is the Rudradhyaya (of the Krishna Yajur Veda).
यदेकमव्ययं साक्षाद्ब्रह्मज्योतिः सनातनम् ।।
शिवात्मकं परं तत्त्वं रुद्राध्याये प्रतिष्ठितम् ।। १५ ।।
The Advaitic imperishable Brahman essence that is ancient, of Shiva, the supreme Truth is enshrined in the Rudradhyaya.
The above is both a teaching of Advaita and also a condensation of the Shvetashvataropanishad.
In the Shvetashvataropanishad one can find many passages from the Rudradhyaya of the Krishna Yajur veda.
Om