Prahlada says in the Srimad Bhagavatam:
श्रीमद्भागवतपुराणम्/स्कन्धः ७/अध्यायः ५
परः स्वश्चेत्यसद्ग्राहः पुंसां यन्मायया कृतः।
विमोहितधियां दृष्टस्तस्मै भगवते नमः ११।
It is due to the Maayaa power of the Supreme Brahman that the ignorant ones get the wrong ideas that 'he is different, I am different'.
Salutations to the Supreme Lord who possesses such a magical power as his Shakti.
स यदानुव्रतः पुंसां पशुबुद्धिर्विभिद्यते।
अन्य एष तथान्योऽहमिति भेदगतासती १२।
When the grace of the Supreme Lord arises, then that false awareness of 'this person is different, I am different' transforms into undifferentiated awareness.
स एष आत्मा स्वपरेत्यबुद्धिभिर्दुरत्ययानुक्रमणो निरूप्यते।
मुह्यन्ति यद्वर्त्मनि वेदवादिनो ब्रह्मादयो ह्येष भिनत्ति मे मतिम् १३।
That One Self alone is transacted variously as 'oneself, he, etc.'. Even the gods such as Brahmaa are deluded in this matter.
From this statement of Prahlada, we know that all distinctions like Jiva-Jiva Bheda, Jiva-Ishvara Bheda etc. are not real, but are imaginary.
अन्य एष तथान्योऽहमिति भेदगतासती | १२।
The above line from the Bhagavata is stated in 1.4.10 of the Brihadaranyaka Upanishad thus:
अथ योऽन्यां देवतामुपास्तेऽन्योऽसावन्योऽहमस्मीति न स वेद यथा पशुरेवं स देवानाम् ।
He who worships a deity other than himself, knowing that deity as separate from himself, thinking 'He is different from me', such a one is without proper knowledge. He remains a beast of servitude to the gods. 1.4.10
In this mantra there is also the teaching of 'Aham Brahmasmi'.
This message of the Upanishads can be found in many texts of Veda Vyasa like Vishnu Purana, Bhagavata etc.
Sridhara Swami's commentary on these verses is given below: