The Mahabharata tells the story of the Pandavas who, on losing their palace to the Kauravas, had to pass through dense forest. While walking for hours ceaselessly without food or water, not only were they tired, they were thirsty too. The Pandavas stopped at one place and advised their youngest brother Nakula to climb up a tree and scout if there was any pond close by. Nakula promptly climbed up a tree and saw a pond not very far away. He climbed down the tree and rushed to the pond to drink water and carry some for his brothers to drink too. Just as he bent down to take water, an invisible voice commanded him to answer some of his queries before drinking the water. Ignoring the voice, Nakula bent down to drink the water but before he could do so, he fell down and died.
When Nakula did not return for long, Sahadeva went out in search of him. He too neared the pond and heard the same invisible voice. He too ignored the voice and collapsed. The same fate awaited Arjuna and Bhima who followed soon afterwards.
At last, greatly worried at not seeing his younger brothers return, Yudhishthira decided to go in search of them. Again, the invisible voice asked him to reply to the queries that he would put to him. Yudhishthira, not to be deterred, decided to reply to the questions and asked the voice to begin. The voice asked, ?What is heavier than earth? What is higher than the sky? What is faster than the wind? What is more abundant than grass??
Yudhishthira gave the following answers that deeply satisfied the invisible voice. He replied, ?Mother is heavier than earth. Father is higher than the sky. The mind is faster than the wind. Thoughts are more in number than the grass.?
The invisible voice was very happy at the answers and revived the four dead brothers of Yudhishthira.
To whom did this invisible voice belong? Yes, it belonged to a yaksha (demon) and as you may be aware, the yakshas and devas fought wars with each other for ages.