Prajnanam Brahma

Prajnanam Brahma (प्रज्ञानम् ब्रह्म, ), a Mahāvākya, is found in the Aitareya Upanishad of the Rigveda. The other Mahāvākyas are "Aham Brahman Asmi", "Tat Tvam Asi" and "Ayam Atma Brahma".

Etymology and meaning
The Sanskrit word Prajñā means "Jñāna or Chaitanya (consciousness)", and spontaneous concept. Brahman is the Absolute, Consciousness, Infinite and "Supreme Truth". Especially "Brahman is Jñāna"; "The ultimate reality is Prajna". "Prajnanam Brahma" means "Brahma-Chaitanya" or "Brahma-Jñāna".

Source and significance
The Mahāvākya is found in the Aitareya Upanishad of the Rigveda. It is mentioned in Aitareya Upanishad 3.3,

"[1] Who is this self (ātman)? - that is how we venerate. [2] Which of these is the self? Is it that by which one sees? Or hears? Smells [etc...] But these are various designations of cognition. [3] It is brahman; it is Indra; it is all the gods. It is [...] earth, wind, space, the waters, and the lights [...] It is everything that has life [...] Knowledge is the eye of all that, and on knowledge it is founded. Knowledge is the eye of the world, and knowledge, the foundation. Brahman is knowing."

- Aitareya Upanishad, 3.3

The third chapter of the Aitareya Upanishad discusses the nature of the Ātman. It declares that Chaitanya (consciousness) is what defines man, the source of all intellectual and moral theory, of all gods, of all living beings, whatever. The Upanishad then claim that the key to the puzzle of the universe is its own underlying. To know the universe, know yourself. Become immortal as you are, Aitareya Upanishad advises.

According to Sahu, ""Prajnanam iti Brahman" - wisdom is the Self. Prajnanam refers to the intuitive truth which can be verified/tested by reason. It is a higher function of the intellect that ascertains the Sat or Truth/Existent in the Sat-Chit-Ananda or truth/existent-consciousness-bliss, i.e. the Brahman/Atman/Self/person [...] A truly wise person [...] is known as Prajna - who has attained Brahman hood itself; thus, testifying to the "Vedic" "Maha Vakya" (great saying or words of wisdom): "Prajnanam iti Brahman"."

According to David Loy, "The knowledge of Brahman [...] is not intuition of Brahman but itself is Brahman."