A guru is so called because he dispels the darkness of ignorance and helps to reveal the self-effulgent Brahman to the deserving disciple. No doubt, knowledge of Vedanta Sastra is essential for one who wishes to propagate it as well as for one desirous of gaining this knowledge. But as the Bhagwad Gita stresses, not all knowers of Vedanta Sastra imbibe the experience of it, pointed out Sri C. L. Ramakrishnan in a discourse. Only realised souls are able to experience Brahma Jnana (the experience of the Brahman) and steeped in Brahma Tatva transmit this highest truth to the ardent seeker.
A jnani experiences the Brahma Tatva in his consciousness at all times. One cannot become a jnani through mere verbal prowess. Only when wisdom always pervades the consciousness can it ignite the spark in another, just as a burning piece of wood alone can cause another to burn. One having mere knowledge without experience of the Atma is as unenlightened as a spoon that serves a delicious food item. The spoon serves the food but it has no idea of the taste of the food. One may theorise about Vedanta Sastra but only when it becomes an experience, he is considered a seer.
The Lord is the primordial Guru to impart the higher wisdom to mankind. Preceptors in human form carry the power to transmit this wisdom. Lord Krishna propounded the essence of the Upanishads to enable mankind search for this truth . When the yearning to seek the truth predominates and the search becomes single-minded , the path becomes visible to the seeker. A teacher draws attention towards specified things or away from particular aspects inviting us to believe in precise truths. The final “seeing” is done by one’s inner eye. Ultimately, one is taught by “Him” who dwells within. Realisation is an inward journey from the perception of the Atma as the body to the discernment of the Atma as the Brahman. There is neither any physical destination, nor is it a search for something tangible in the universe. It is the awareness of the self-effulgent truth, an understanding that what is sought is already within.