Katha Upanishads is one of the popularly known Upanishads that gives more insight in knowing the Brahman.  Naciketa is the son of Vajrashravasa. The latter is considered to be one of the famous sages and is known for his charity.  One day when Vajrashravasa was giving charities, Naciketa noticed that all his father was giving were of inferior quality with no value.  He saw his father giving sick and old cows that do not yield milk at all.  Charity means helping others with what they need.  Any charity with pomp and vanity is not charity at all.  The person who receives charity should also be a deserving one.  Though Naciketa was young, he was very intelligent.  Visibly upset over his father's action he asked his father to whom he would give him (Naciketa) in charity.  His father answered that he would give Naciketa in charity to the God of death, called Yama.  Naciketa decided to fulfill the wishes of his father and left for Yama's abode.  When he reached Yama's abode, he was made to wait without food and water as the Lord Yama was not available at that time.  When Yama returned from his sojourn he apologized to Naciketa for having made him to wait without food and water and in return Yama promised three boons to Naciketa.  Extending a hearty welcome to any visitor is underlined here.

Naciketa asked the following three boons from Yama.  The first boon was that his father should not be angry with him and that when he returned to his father, his father should accept him with love and affection and that his father should not feel his absence.  The second boon that Naciketa asked Yama was about the knowledge about agni or fire to reach the Heaven.  Fire sacrifices are very popular In India and other countries.  Agni is supposed to be the carrier of our wishes to the God.  The third boon he asked Yama was about the soul.  Yama clarified all the doubts of Naciketa since Yama is an exponent in Vedas and sastras.

The first boon that Naciketa asked Yama shows his concern for his father.  In spite of his father having said that he would sacrifice his son to the lord of death, Naciketa still expressed love for his father as he knew that his father would have said that without meaning it seriously.  Since Naciketa wanted to keep up the words of his father, he had chosen to go to the lord of death.  Apart from emphasizing the truth, it also means that a son has a duty to keep up the promises of his father and also to make him happy.  That is why Naciketa asked Yama to keep his father happy till he returned back to his father.  Therefore the first boon emphasizes the duties of a son to his father and also the importance of truth.

The second boon was about knowing the Heaven.  Naciketa says that people in the Heaven do not have fear of death as the lord of death Yama is not there.  Those people do not feel hunger and thirst.  They do not have any worries and they live in happiness.  The people live there have divinity.  Having addressed Yama like this, Naciketa wanted to know about the fire ritual that could take anyone to the Heaven by performing it.   He demands this knowledge from Yama saying that he is always sincere and dedicated in acquiring knowledge.  As Yama already knows Naciketa and his qualities, he readily shared his knowledge with Naciketa.  There are two things that are clear at this stage.  One is that knowledge should be shared and secondly, only with those who are really interested in acquiring knowledge.

Avidya or ignorance about the Brahman is the cause for destruction, as it leads to desires and attachments. Knowledge about the Brahman leads to liberation. Liberation does not mean going to the Heavens, but merging with the Supreme creator. To attain liberation, renunciation is important. If you renounce, where is the question of desires and attachments. When you renounce, you do not discriminate. When there is no discrimination, you are nearing Brahman, as Brahman does not discriminate. If someone thinks that there is a short cut to self-realization, unfortunately they reach the abode of Yama only. This means they have to be born again. Same is the case for making money. If you want to make quick money, that is just impossible. The quick money if made will also go away quickly. Only the money earned out of one's own work will stay. The quick money always prompts you to indulge in wrong activities. Another aspect is attachment to one's family. This is a ticklish issue to resolve. If you have a family, it is your duty to make them happy. Assuming that you want to be a bachelor, still you have your parents and if you do not maintain them properly at their old age, your karmic account swells. Having born, all of us have certain duties to perform, but the results of the duties should be given to the God, be it good or bad. Therefore such types of desires and attachments make us not to think about the Brahman. Such people do not think about life after death. Again only humans can think whereas other creatures cannot even think. Thinking is one of the products of mind. Without mind you cannot gain knowledge. Therefore knowledge is applicable only to the humans and not to other living beings. This is the reason for saying that the human birth is the gift of God.

Yama says that supreme Self cannot be realized by reading scriptures, listening to lectures, attending classes etc. The Supreme Self can be realized only through teachings of a learned and self-realized guru. Yama also says that such gurus will be too happy to have disciples like Naciketa, a disciplined and dedicated pupil. Yama told Naciketa that he (Naciketa) knew what self realization is, but his knowledge of self-realization is not complete as he has this knowledge not due to internal search. When you try to explore within, you get many doubts, for which you may not have an answer. Such doubts can be clarified only by a competent guru.

The atman exists everywhere.  It (atman or Brahman) is there in akash in the form of the sun (used for comparison only).  It (Brahman) is the base of everything in this universe (every activity in the earth is based on the sun).  It is there between the earth and the heaven, it is there in air, fire, earth, as guests at home (atiti), lives in a cave situated in our heart (not the biological heart), it is in all the deities and gods (meaning various types of energies), it is there in the truth, it manifests in fire rituals, it manifests in the earth, it manifests in the mountain.  The Supreme Self is the biggest of all says Yama.  This statement of Yama is to emphasize the fact that Brahman exists everywhere.  It is in the form of jivan or soul which makes the prana (life energy) goes up and makes the apana goes down in our body.  (The friction that takes place when prana and apana meets produces energy and makes the kundalini ascend) This (the soul) is in centre of the body (the heart chakra in the spinal cord) and other parts of the body look upon to it for their functioning.  Here Yama talks about soul and not the atman, because the activity of moving prana and apana is associated with atman.  If this soul or jiva leaves the body, what remains is what Naciketa is seeking.  The secretive meaning of this statement is that Brahman exists in dead bodies too.   Brahman remains even after the body is burnt or buried.  But no living being lives solely on prana, apana, etc.  They live on the strength of the atman only.  That is why atman is compared to the sun.

Yama then proceeds to explain the position of the soul after death.  After death some of the souls enter human bodies.  Some souls become plants, etc.  The rebirth of the soul depends upon one's karma alone.  When we enter the stage of deep sleep, our senses do not function.  Though our senses do not work, the atman remains awake.  It never sleeps.  It is eternal.  When we had a good sleep, next day morning we say that we had a good sleep.  When we were in the stage of deep sleep, how we can say that we had good sleep?  This is because the atman within did not sleep, was witnessing our act of deep sleep.  This is a typical example of how atman never participates in our activities, and remains only as a witness.  Yama tells Naciketa that is the atman which he was seeking for.  Atman is compared to fire.  The fire takes different shapes and forms.  The flame of a candle is different from the flame of a gas oven.  The fire of a welding machine is different from the fire of a furnace.  But the nature of the fire remains the same.  In the same way, atma is the same, but it takes different shapes according to the form of the being.  Atma taking different shapes means atma is covered by different gross forms.  Atman or the Brahman is the innermost of any living being and all other things form protective coverings.  For example atma is the same in a tree as well as in a human.  The external shape alone is different such as tree or human and the atman inside is the same in both.  But it must also be remembered that atma also exists outside a tree or a human.

This atman is covered by maya or illusion which misleads us from knowing the atman.  As long as you are not able to remove the veil of maya, Brahman can never be realized.  As long as maya exists, the duality continues.  As long as duality continues, you have fear and associated miseries.  But by removing the veil of maya, you realize the Brahman and if you further realize that you are one with the Brahman, where is the question of fear, sufferings, miseries, etc?    Then there is comparison between happiness and sorrow.  A comparison can be made only between two objects.  When there is only one object with which can it be compared?   Yogis have said that they had seen the Brahman.  How can they see the Brahman when we say that Brahman does not have a form?   Naciketa wanted an answer for this from Yama.  He wanted to know whether the divine vision happens outside our body or inside of our body.  Yama says the vision of divinity is neither external nor internal.  It is called bliss and it is to be experienced and cannot be seen.  Bliss cannot be explained by words as your experience will be different from mine.  Further it is beyond words as it is the rendezvous with the Brahman.

Everything functions out of fear for the Brahman.  He never expects anybody to break the laws as He Himself does not break the laws made by him.  The law of karma is called the law of the Lord.  Brahman never grants you anything that is outside the purview of your karma.  Brahman is like a coin.  Both sides are not the same.  In the same way, on one side Brahman is kind and gracious.  On the other side he is a strict disciplinarian.  That is why He is terror to those who break the law of Nature.

When your mind is totally free of duality, the divinity begins to dawn on you.  If you are still associated with your senses, there is no way you can realize the Brahman.  If you do not realize the Brahman you are going to die to be reborn as a human or an animal or a plant or it could be anything.  Mind is powerful than the senses. Intellect is powerful than mind.  Soul is powerful than the intellect.  Maya or illusion is powerful than the soul.  But the Brahman or the Supreme Self is all powerful and nothing can be compared to Him.  God cannot be seen with the external eyes.  He can be realized as the Brahman in the form of light only within.  He can be realized only if the mind is clear or inactive.  When mind is inactive, it means that it is not attached to the senses.  If it is not attached to the senses, mind has time to look within, with the help of knowledge.  Therefore, the basic requirement to realize the Brahman is the capacity to manifest with the help of knowledge.  You can manifest only if you have sufficient practice.  You can practice manifestation of the Brahman only if your mind is not associated with external objects.  The one who realizes this becomes immortal.  At the time of his death, his soul leaves his body through the orifice at the top of the head.  In others, the souls leave through the remaining ten openings.  They are born again.  You must learn to separate this self illuminating atman from your body and realize it.  This is called Naciketa vidya.   By saying this, Yama concluded his teachings to Naciketa.   This is considered to be the master piece on soul and the Brahman, as these are the words of the Lord of death, Yama.