Knowledge of the Self can be attained only by the grace of the Guru or the spiritual preceptor. The knowledge is transmitted from the preceptor to disciple.
You can know the unknowable (Brahman) by purifying your mind, by serving a Guru who is a Brahmanishtha (established in truth), by getting lessons from him and by meditation.
A medical student is in urgent need of a Professor of medicine. A Junior Vakil needs the help of a senior advocate for his guidance. A junior cook needs the help of a senior cook. When such is the case with worldly matters, what to speak of adhyatmic spiritual subjects which deal with hidden, subtle Atman! The help of a Guru who has realised the Self is imperatively necessary for the aspirant for his guidance. Otherwise he will be groping in the thick forest of darkness, of ignorance.
The aspirant gets obstacles or impediments, dangers, snares, pitfalls on the spiritual path. He will have to be very careful in sadhana also. A Guru who has already trodden the path and reached the goal is very necessary to guide him.
Young aspirants should always live under the guidance of a perfect Guru for some years. They should be under subjection. They should learn perfect obedience and humility. If they have their own ways, they become arrogant and conceited. They do not make even an iota of progress in spirituality.
In nature no two trees are alike; no two leaves are alike; no two persons are alike; no two vibrations are alike; no two temperaments are alike; no two minds are alike. Therefore there are various ways for controlling the mind to suit people of different temperaments. Each can have his own way of sadhana. For yourself if you are not able to chalk out the path, get it from a Guru or preceptor. Learn Yoga under a Guru. Then only you will be able to understand the subtle points of Yoga. He will inspire you when you are depressed, will remove your doubts when you come across stumbling blocks on the path, and show you the right path because he has already trodden the path himself. If you are sincere and earnest, the Guru’s grace will flow to you like Tailadhara a continuous flow of oil. He will infuse energy, love, wisdom and spiritual current if you have true receptive attitude, sincere faith and devotion to him. Now stick to one path and one Guru. Do not waver. Be patient. Be sincere.
Aspirants do not possess unshakable faith in the Guru or Srutis. They have half or wavering faith. That is the reason why they fail in attaining success in Yoga or Jnana.
The Lord and the Guru are both one. Try to see the Lord in your Guru. Then only you will have progress in the spiritual path. Then only you will attain Self-realisation. If you try to see defects in your Guru, you will not be benefited in the least. Guru is your father…your mother…your saviour. Guru is your sole refuge and support. Therefore revere your Guru as the Lord Himself.
The real aspirant should drink the charanamrita of his Guru, should take the Guru’s ucchishta, should meditate on the form of his Guru as Brahman Himself and should do Japa of his Guru Mantra constantly. Then he will have Self-realisation easily.
The duty of a soldier is to obey implicitly the commands of the commander. He must not question anything. Even so, the duty of an aspirant is to obey implicitly the orders of his Guru. Then only he can grow quickly in the spiritual path.
He who is devoted to his Guru and has done upasana can only comprehend the depths of the teachings of the Vedanta. You will find also in Svetasvatara Upanishad: “Whoso hath highest love for God and for the Guru as for God, to that Mahatman, the truths here taught shine in full.” Section VI-23.
The teachers in this world is said to be of three kinds, viz., the one who commands, the one who imparts knowledge, and the supreme one who gives release. The one who commands shows the way; the one who imparts knowledge teaches the supreme place; and the one who gives release reveals the supreme truth, knowing which you will attain immortality.
The people after crossing a river, wanted to see whether all the passengers were alive. But each of them counted all the nine others except himself, and found that one was missing and all began to weep bitterly for the loss of one of them. At last they were disillusioned by some one telling each of them that the reckoner himself was the tenth.
Just as the iron filings are magnetised in the presence of a magnet, so also aspirants are magnetised when they are in close contact with their masters or Gurus. Just as iron is transmuted into gold by the touch of philosopher’s stone, so also persons with evil tendencies are transmuted into veritable saints when they come in close contact with sages and Yogins.
When a Guru is in the physical body, he can help the aspirants and disciples more. If the disciple has faith in his Guru, he will help him even after he has abandoned his physical body. Sri Sankara, the propounder of the Advaita philosophy, Sri Dattatreya, Sri Jnana Dev of Alandi even now bless the aspirants who have devotion unto them. They have no body on earth but yours, no hands and feet but yours. Yours are the eyes through which they behold this universe. They move about through your feet and do good to the world.
Reference: The Divine Life Society website