Maha Vakya

प्रज्ञानं ब्रह्म (pragñānam brahma) Knowledge/Consciousness is Brahman Aitareya Upanishad Rgveda
अहं ब्रह्मास्मि (aham brahmāsmi) Iam of Brahman Brhadāranyaka Upanishad Shukla Yajurveda
तत्त्वमसि (tat tvam asi) You are It Chandogya Upanishad Samaveda
अयमात्मा ब्रह्म (ayamātmā brahma) This Atman is Brahman Mandukya Upanishad Atharvaveda