The request sounded too small for the king offering it.
Vāmana, appearing as a dwarf brāhmaṇa, came to the sacrifice of Bali. Bali welcomed him and offered wealth.
Ask for land. Ask for cattle. Ask for what you need.
Vāmana asked for only three paces of ground.
Bali thought the request showed how little the young petitioner understood his opportunity.
Why ask for three steps, he said in effect, when the giver can provide an entire region? A person who comes to me should not have to beg again.
Vāmana answered that someone who cannot be satisfied with three steps will not necessarily become satisfied with a continent. Desire can keep enlarging after possession enlarges.
Bali agreed to the small request.
Then his teacher Śukrācārya intervened.
Śukrācārya had recognized the dwarf.
This was Viṣṇu.
And the three steps would not remain the steps of a small body.
He warned Bali plainly. With one step, Viṣṇu could take the earth. With another, the higher regions. Once the form expanded, where would there be any place left for a third step?
The warning went further: if Bali promised what he could no longer deliver, the promise itself would fail. His wealth, position and livelihood would be endangered.
Śukrācārya advised him to withdraw.
This is the point that prevents the episode from becoming a simple story about a careless king being tricked by a tiny visitor.
Bali now understood the danger before completing the gift.
He answered that poverty, loss of position and even death frightened him less than speaking falsely after giving his word.
If the visitor truly was Viṣṇu, Bali did not see that as a reason to become less truthful.
He completed the gift.
Then Vāmana changed.
The dwarf form expanded until it filled the universe. Bali and those around him saw the worlds contained in that vast body.
The first stride covered the earth.
The second reached through the higher worlds.
Everything Bali had claimed the power to give was already contained in two steps.
There was nowhere left for the third.
Bali was bound and confronted with the unfulfilled remainder of his promise.
He did not answer that the bargain had become unfair.
He did not say that two cosmic strides should count as three ordinary ones.
He offered what remained under his control.
His own head.
Place the third step here.
The Bhāgavata's resolution does not reduce Bali to a loser who has simply been outsmarted. His steadfastness is honoured.
He is given Sutala to rule, and the relationship with Viṣṇu continues under protection rather than ending in abandonment.
That is why the story holds two ideas at once.
Vāmana is the one who reveals how little three steps can mean when the measurer changes.
Bali is the one who reveals what a promise means when the cost changes after the words have already been spoken.
A child can still argue with his decision. The source itself gives Śukrācārya a serious argument for limits, livelihood and prudence.
But Bali hears that argument before he chooses.
Bali's answer to Śukrācārya is not a claim that the warning must be mistaken. He accepts that the giver may lose wealth, rank and even safety. What he rejects is the idea that those losses are worse than becoming a person whose pledged word cannot be trusted.
When Vāmana expands, the Bhāgavata lingers on the universal body: land, sky, seas, beings and the worlds appear within it. The small request has not secretly changed wording. The meaning of a 'pace' has changed because the one taking the pace is now revealed in cosmic measure.
After Bali offers his head, the ending keeps developing. His grandfather Prahlāda appears, Bali's steadfastness is praised, and Vāmana assigns him Sutala rather than leaving him without a place. He also promises protection there. Loss of the three worlds is therefore followed by a different form of honour and nearness.
Bali's promise becomes his only remaining possession, and he keeps giving until even the third step has somewhere to land.