Vamana (means dwarf) Avatar was the fifth incarnation of Lord Vishnu that took place in the Treta Yuga. It was the first incarnation of Vishnu as a human being. He took back the kingdom of gods from Asura king Bali and gave it back to Indra.
The Story of Vamana Avatar:
Most of the story is based on the story in the Vamana Purana.
Background:
King Bali was the grandson of Prahlada and the son of Virochana. King Bali (also known as Mahabali) performed a penance to please Lord Brahma and got a boon to be undefeated in any battle. After that, he attacked the heavens, defeated the gods, and drove Indra and other gods out of heaven. Soon, he became the master of three worlds. King Bali, unlike other Asuras, was a noble and kind-hearted person. He was very just to his subjects and used to take good care of them. Hence, all his citizens were very happy with him.
The Birth of Vamana Avatar:
On the other hand, being defeated by Asuras, the gods were wandering here and there and were gloomed by the popularity of King Bali. Especially, Indra was very sad as he was unable to defeat King Bali. Aditi, the mother of the gods, understood the problem behind his sadness and performed a penance for 10,000 years to please Lord Vishnu. Aditi asked Lord Vishnu to get the kingdom of gods back from Bali and give it back to Indra. Lord Vishnu accepted her request. Aditi got pregnant, but soon after her pregnancy, the earth shook violently because of the unbearable weight of the fetus. Wherever she went, that particular portion of the earth tilted down because of the enormous weight. Her pregnancy had significantly eroded the radiance of the demons.
This worried Bali and he asked about the reason for his grandfather, Prahlada who meditated upon Lord Vishnu and found that he would be taking birth as Aditi’s son. When he told the same to Bali, the arrogant king insulted Lord Vishnu. Therefore, Prahlada cursed him by saying, “How dare you to say like this! I am ashamed that you have taken birth as my grandson. I curse you to lose your kingdom and fall from grace because you have criticized Lord Vishnu- the supreme savior.”
After some time, Lord Vishnu was born as Aditi’s son.
Bali’s Yajna:
Once Bali had organized a yajna and announced that he would give anything to anybody on that particular day. Soon, the Brahmin Vamana reached the place. He was carrying a kamandalu and a wooden umbrella with him. Bali asked him what he wanted. Vamana told him to give him only three steps of land measured by his own feet. Bali happily agreed to that.
Before accepting the donation, Vamana tilted his kamandalu to pour water into the hands of Bali. Recognizing that Vamana was not a common person and was Lord Vishnu himself, Shukracharya, the teacher of Asuras, took the miniature form and blocked the nozzle of the kamandalu. Vamana realized the trick of Shukracharya and pushed a wooden stick inside the nozzle, saying that an insect could be blocking the flow of water. This stick pierced one eye of Shukracharya and he became blind by one eye.
Lord Vishnu Sends Bali to the Netherworld:
Bali drank the water from kamandalu after that. Soon, Vamana grew into a giant size of cosmos. In his first step, he covered the whole earth. In his second step, he covered the whole universe. Now, there was no place left to place his third step. So he asked Bali where should he keep his third step. Bali recognized that Vamana was nobody but Vishnu himself. He told him that the only place left was his head where Vamana could put his third step.
So Vamana put his third step on the head of King Bali and pushed him into Patala (netherworld). The giant form of Vamana is also known as Trivikrama Avatar. Pleased by the generosity of Bali, Vishnu made him king of the netherworld and blessed him with immortality. He allowed him to come to the earth once a year and meet his people. Onam festival is celebrated when Bali returns to earth once a year.
Without Bali, Asuras became weaker and Indra regained his kingdom of heavens.
If Bali was so Noble, Why did Lord Vishnu Deceive Him?
There could be three possible reasons behind this.
1. Because Lord Vishnu had given the boon to Aditi that he would give heaven back to the gods, he had no other option. He did not kill Bali because he was a good ruler. So he just pushed him into the netherworld.
2. There is another version of the story of Vamana Avatar. Although King Bali was noble for his people, he was still a hater of Vishnu. He was very shrewd; by offering prosperity to people, he was wiping out their devotion to Vishnu.
Long ago, the mother of Shukracharya (teacher of Asuras) was accidentally killed by Lord Vishnu when she was giving shelter to demons. Hence, Shukracharya became his enemy. He advised Bali to wipe out Lord Vishnu’s devotion from the heart of the people deceitfully instead of forcefully. So Bali was doing the same thing as Hiranyakashyapu did in another way. Hence, Lord Vishnu also deceived him instead of defeating him in a war.
3. Mahabali was invincible in any battle because of Lord Brahma’s boon. Therefore, he had no other option.