The Upanishad discuss the metaphysical concept of Brahman in many ways, such as the Śāṇḍilya doctrine in Chapter 3 of the Chandogya Upanishad, among of the oldest Upanishadic texts. The Śāṇḍilya doctrine on Brahman is not unique to Chandogya Upanishad, but found in other ancient texts such as the Satapatha Brahmana in section 10.6.3. It asserts that Atman (the inner essence, Self inside man) exists, the Brahman is identical with Atman, that the Brahman is inside man—thematic quotations that are frequently cited by later schools of Hinduism and modern studies on Indian philosophies.Chandogya Upanishad with Shankara Bhashya Ganganath Jha (Translator), pages 150–157For modern era cites:
