When sage Suka explains to Parikshit the incarnation of the Lord as Vamana, he points out that He was born with the divine identification marks — four arms, conch, discus, etc., and that He transformed this divine form into that of a short-statured Brahmacharin (Vamana) in the manner of a stage actor who changes his appearance to suit the role play he adopts. He who is the sole and unquestioned Lord of the entire creation adopted the stance of a seeker to fulfil Aditi’s desire to see her sons, the Devas, back in their abode that had been taken away by the Asuras.
The Lord chose a diminutive appearance. This is because the very act of seeking favours from others places one in a delicate situation regardless of the status of the seeker, Sri N. Rama Dikshitar said in a lecture.
Hearing about the Asura king Bali’s Aswamedha sacrifice, the Lord entered the sacrificial campus, diminutive but ever so resplendent. The assembly of sages and other deities automatically stood up to greet Him. What a God-sent opportunity, thought Bali, to honour such a deserving guest whose effulgence was singularly attractive. When Bali was ready to give this guest whatever was desired, the Lord surprised him with a trivial request — three paces of land measured by his own feet — that hardly matched Bali’s generosity. Bali urged Vamana to ask for something more that would sustain Him for a lifetime.
The Lord now spoke of contentment as a state of mind. This comes with mastery over the senses and is capable of giving lasting joy. In contrast, even gaining the entire universe will keep a dissatisfied mind craving for more. One should receive as gifts only what is essential.
Bali’s preceptor Sukra easily saw through the Lord’s plan to settle scores with Bali and warned the king. But Bali’s sense of moral responsibility led him to ignore Sukra’s advice .
The Lord now revealed His spectacular, never-before beheld form as Trivikrama who measured the entire universe with a mere two paces and queried Bali where to place the third. Bali was humbled but remained unshaken and offered his head to the Lord. Bali gained enlightenment through downfall.