"Learning never stops"- J. Krishnamurti

There are three kinds of gurus:

(1) the siksha guru, a person who instructs;

(2) the diksha guru, a person who initiates with sacred mantras; and

(3) the Lord in the heart, who is properly accessed through the prior two. 

There is a famous story of King Yadu and Avadhuta which is as below:

King Yadu observed how this young man had had a peaceful and joyous demeanor, even though he didn't have any of the usual amenities of life. Yadu asked him how this was so: “Why are you so happy, despite having little facility and no material acquisitions?”

The avadhuta answered that he was fortunate enough to have had many preceptors who had shown him the way. And with that, the avadhuta began to describe each of these teachers one by one, along with the lessons he had learned from each. The first five are the principal material elements: earth, air, fire, water and ether.

1. 1. The earth: The avadhuta said, “From the earth I learned that when one is overcome by the elements of material nature through one’s destiny, one should not swerve from the spiritual path. From the earth’s trees and mountains I have also learned to be selfless, and so I am ready to act for the benefit of others, like the trees.” His statement is reminiscent of Chaitanya Mahaprabhu's verse: “One should chant the holy name of the Lord in a humble state of mind, thinking oneself lower than the straw in the street; one should be more tolerant than a tree, devoid of all sense of false prestige, and should be ready to offer all respect to others. In such a state of mind one can chant the holy name of the Lord constantly.”
2. 2. The Air: His second guru was the air. A yogi, he said, interacts with the sense objects, just like the air does. Just as the air does not become attached, neither does the yogi. Sometimes the air takes on the odors of the earthly objects it passes over or through. However, it simply carries the odors, never becoming like the objects it passes. In this way, the yogi is unaffected by the world around him, even when, to others, he appears to have taken on its qualities; this is because he knows that he is ultimately transcendental to it.
3. 3. The Sky: His third guru was the sky, from whom he had learned about the all-pervasive nature of the soul and how it is equal to all. The sky treats all moving and non-moving beings in the exact same way. Similarly, the true yogi recognizes that God is present in all beings equally, and thus makes no distinctions between them.
4. 4. Water: The avadhuta’s fourth guru was the water, which teaches us through its natural purity and purifying qualities. In its original state, water is transparent, clear and refreshing. Saintly persons are also like this. In addition, he said, they transform and cleanse wherever they flow. One on the spiritual path should be the same way. 
5. 5. Fire: From fire, one can learn how to remain unaffected by the things one consumes. Yogis continue with their practice regardless of the state of their digestion. This is not to say that what one eats is unimportant; it is very important. There are certain foods that instigate poor digestion, making it difficult to pursue yogic practice, such as meat-eating. That being said, one must continue with one’s practice regardless of the food one finds oneself eating – in other words, regardless of circumstance. The constant flux of the world should not affect one’s discipline, as fire is unaffected by what it burns. Fire burns whatever is in its midst, but still it remains fire. Another lesson the avadhuta took from fire: never accumulate material acquisitions. Burn through them as needed, but never hoard.
6. 6. The Moon: The avadhuta’s sixth guru was the Moon. The Moon goes through various phases during its monthly cycle, but its fullness or darkness at the beginning and end of each fortnight are only appearances – the Moon itself remains unchanged. Similarly, each of us is a spiritual being that essentially remains unchanged, despite the various permutations of the body. As Krishna says in the Bhagavad Gita (2.13): “Just as in this body we all must pass first through childhood, then youth and then old age, at death we simply take another body. Such a change does not disturb the minds of those who know the truth.” 
7. 7. The Sun: The next guru was the Sun, which evaporates large quantities of water with its potent rays. In due course, however, the Sun releases this water to the Earth in the form of rain. In the same way, a practitioner may make use of all types of material objects, but they eventually redistribute them to whoever might need them. The Sun thus provides a lesson in detachment: how to use whatever comes one's way in Krishna’s service, and then relinquishing whatever one has to those in need.
8. 8. The Pigeon: The avadhuta brahmin next spoke of his eighth guru: a pigeon. Once, he said, there was a pigeon that lived in a forest along with his wife. He built a nest in a tree and lived there with her for some years. The hearts of the two pigeons were bound together in every way. Naïvely trusting in the future, as lovers do, they enjoyed their lives as a couple, expecting many years together. Eventually, the female pigeon became pregnant, and soon her nest filled with eggs. As time went on, the two pigeons shared their love with their children, taking great pleasure in listening to their chirping. All was good. Then, one day, the pigeons went out to find food for the children. During their absence, a hunter saw the little nest with the baby birds. He spread his net over them and captured them all. When the adult pigeons returned, they saw what had happened. Distraught, the mother cried piteously and rushed toward her offspring. Her judgment compromised by grief, she rushed toward the net to free her helpless children, thereby causing herself to be trapped as well. Seeing the plight of both his children and his wife, who were as dear to him as life itself, the father pigeon began to lament without control. The pain was so intense that he lost all will to live. Bewildered by the sight of his family struggling in the net to survive, he, too, lost consciousness, falling into the hunter’s grasp. The avadhuta concludes from this story that too much material attachment leads to disillusion and suffering. Life in this world is full of risk, and one's attainments will surely come to an end, for even the greatest of material pleasures – love, family, and so on – are temporary and limited, and a spiritual practitioner must constantly be aware of this. 
9. 9. The Python: The ninth guru was the python. This great snake, it is said, lies quietly for long periods of time without food. It does not search desperately, like other animals in the wild, but rather it waits for its prey to come within range. If nothing appears in its midst, it is capable of tolerating hunger. In a similar way, said the avadhuta, we must be able to tolerate inconveniences without being disturbed, focusing our mind and attention on the Supreme.
10. 10. The Ocean: The ocean can also be considered a guru. It teaches us that one should not be disturbed by the thoughts and desires that consistently plague the mind. In the rainy season, rivers will enter the ocean without raising its level. And in the dry season, rivers are reduced to almost nothing, but the ocean’s level is not diminished. In a similar way, a self-realized sage should remain equipoised in all circumstances, due to an awareness of his eternal spiritual identity. Krishna makes this same point in the Bhagavad Gita (2.70): “The ocean is always being filled by the rivers that flow into it, but it remains deep and unchanging. Similarly, one who recognizes that sensual desires are constantly flowing into him can attain peace, but not the person who increases his desires by attempting to fulfill them all.” 
11. 11. The Moth: The avadhuta observed the following truth from the moth: just as this nocturnal insect is drawn into the alluring light of the fire to meet its death, so, too, do sense objects attract all living beings with their beauty, but can lead instead to destruction. In the Bhagavad Gita (11.29), Lord Krishna also uses the example of the moth to describe how all creatures are drawn into the fire of death. “Just as moths rush into the bright flames of the fire, meeting their destruction, so too do all these worlds rush with great speed into the mouths of your universal form, there meeting their death.”
12. 12. The Honeybee: The bee goes from flower to flower, taking just a sample of what each has to offer. However, if the bee becomes greedy, enjoying too much honey, it risks being trapped after the Sun sets, when the flower’s petals close. Material life teaches a similar lesson. Sense gratification is like salt: too much spoils a food preparation but too little does as well. One must learn the art of taking just enough, and spending the balance of one’s time for life’s real purpose: self-realization.
13. 13. The Elephant: In the same way that the moth is led to its own destruction, the avadhuta tells us, the elephant is also defeated by his own desire. In India, wild elephants were typically captured by using she-elephants to lead them towards a pit, into which they would fall. The lesson here, once again, is that a renunciate should not allow himself to be influenced by attraction to the opposite sex which is a great bane on the spiritual path.
14. 14. The Honey Gatherer: In ancient India, there were those who specialized in gathering wild honey from hollow trees and other places where bees made their hives. The avadhuta said to the King, “Some misers are like bees who gather honey and store it away. They do not attempt to enjoy it themselves, nor do they share it with others. Eventually, someone else comes along and takes everything they have, like the honey-gatherer who takes all the bees’ accumulated honey for his own purposes. In a similar way, traveling mendicants approach those living in the world and ask for charity. This gives them the chance to engage their wealth in productive ways that will bring them eternal benefit.” In this way, the avadhuta saw purpose in the householder's hoarding of material acquisitions – saintly people can come along and make good use of them. 
15. 15. The Deer: In ancient India, hunters would play a flute or some other musical instrument to attract deer. Once the animal approached, enamored by the sound, they would kill it. Learning from this example, a spiritual seeker should avoid mundane songs or gossip, for these, too, will serve merely as distractions from the goal, constituting a form of spiritual death.
16. 16. The Fish: The lesson given by the fish is similar. Here we are warned not to be too enticed by delicious foods. The fish sees the bait, but not the hook. Of all the senses, the avadhuta tells us, the tongue is the most difficult to control. Someone who has been able to overcome the other senses might still be tempted by the tongue. Therefore, Vaishnava texts recommend controlling the tongue by chanting God's names and eating only prasada, or food that has first been offered to Krishna in sacrifice. In this way, one can avoid the fate of the fish.
17. 17. The Prostitute, Pingala: Next is the story of Pingala, the avadhuta’s seventeenth guru. Pingala is distinct among the Bhagavata’s 24 teachers in that she teaches with words rather than mere example. She lived in the ancient city of Videha, where she would stand in front of her house watching men as they passed by. Her motive was to determine whether they were prospective clients or not. “Does this fellow have money? That one looks wealthy. Will he be able to pay me?” On one particular night, she found herself without a single customer, and, gradually, she lost hope that anyone would require her services. Because of this, she became morose and forlorn: how would she pay her bills? What if she were no longer desirable and this dry spell continued for many days? All of a sudden, despite her anxiety, she realized that she did not mind the lack of business, since she was beginning to feel detachment. In fact, she realized that she was experiencing a feeling of freedom and joy. Finally, she broke out into song. The lyrics, as conveyed in the Bhagavata, reveal the foolishness of prostitution, of sex desire,of the bodily concept of life. She sung of the temporary nature of material pleasure, and how, for some unexplained reason, she could now see all this, and of how she finally became privy to the mercy of the Lord.
18. 18. The Falcon: The avadhuta then told the story of the falcon, or the kurara bird. One day, a flock of falcons went in search of food, and one fortunate falcon caught a mouse. Unfortunately, the other falcons were not so lucky, and so they flew after the first one, hoping to usurp his prize. When he saw what was happening, he immediately dropped his prey to fly off and save his own life. In doing this, even though he lost his food, he felt surprisingly peaceful. “Accumulation of material things leads to misery,” said the avadhuta. “One who knows this becomes akinchana – someone with the deep realization that nothing is truly his, for everything belongs to God.” 
19. 19. The Innocent Child: “There are two kinds of people who are free from worry,” the avadhuta said next, introducing guru number nineteen. “One is the fool, a person who is simply bewildered and unaware. The other is the sage – a person who is beyond the entanglements of material nature. In any case,” he continued, “It is important to be indifferent to praise and insult, to have no worries for wife or family, to take pleasure and joy in one’s own being, with simplicity.” In this way, the avadhuta suggests we learn life’s secrets from the mood of an innocent child. 
20. 20. The Marriageable Daughter: There was a young girl of marriageable age who also played the role of a guru. The avadhuta witnessed a situation in which such a girl’s parents were looking to get her married. One day, however, when she was home alone, several suitors came knocking at her door, making their intentions known. Since no one else was there, she herself had to greet them. Although she invited them in, she rushed off into the kitchen, to prepare a meal for them. While there, her wrist bangles made loud noises, banging together as she moved the pots and pans. Not wanting to disturb her guests, and not wanting them to think that she was a low-class woman who must cook for herself, she gradually removed her bangles one by one, leaving only one pair on each wrist. Nonetheless, when she began cutting vegetables, she found that the bangles still made a harsh sound, so she slipped another off each wrist, leaving only one. From this, the avadhuta concluded that it is best to live alone. If one spends too much time with crowds, it can cause a distraction from spiritual life, and if one even has only one other associate, it can still cause a disturbance. Those who are serious about the path, he concluded, live alone, or they live with others who are also serious about the path. This is another way of living alone. 
21. 21. The Arrowmaker: The avadhuta once observed an arrowmaker who was so absorbed in his work, sharpening arrows, that he did not notice a parade passing by his workshop, even though it included a great king and much pomp and celebration. He was too focused to even raise his head. Similarly, says the avadhuta, a yogi should be so absorbed in the Self that he does not care about anything else going on around him.
22. 22. The Snake: Evoking a lesson similar to the one involving the marriageable daughter, the avadhuta directs our attention to the snake: Here, we again learn the importance of living alone, without any fixed home or dependence on anyone. He says that snakes are happy to slither into and out of any residence, and come and go without attachment. Spiritual practitioners should be the same way.
23. 23. The Spider: The spider emits its thread from its own body, creating a complex web, and then it draws the thread back into itself. Similarly, God creates the universe out of His own being and, when the work of creation is completed, He draws it back into himself. Here our twenty-third guru teaches us something about the nature of God, rather than how to live in the world, but it also speaks to the quality of non-attachment.
24. 24. The Wasp: Once, a wasp trapped a weaker insect in its lair. Out of intense fear, the lesser insect took on the mentality of a wasp, for it could only think of its captor and nothing else, and thus it became a wasp in its next life. This teaches us that we attain our future births according to that which we fix our minds upon.