Mahavakya
Mahavakya, or “the great sentences”, state the unity of Brahman and Atman. They are four in number and their variations are found in other Upanishads.
1 Prajñānam brahma – Brahman is knowledge – aitareya upanishad – Rig Veda
2. Aham brahmāsmi – I am Brahman – brihadāranyaka upanishad – Yajur Veda
3. Tattvamasi – That thou art – chhandogya upanishad – Sama Veda
4. Ayamātmā brahmā – This Atman is Brahman – mandukya upanishad – Atharva Veda