Yudishtra had equanimity of temper, which enabled him to be calm and contemplative even in situations in which others would be emotional said V.S. Karunakarachariar in a discourse. He finds his brothers lying dead on the banks of a pond, and yet when he is asked to answer questions by a Yaksa, he agrees to do so. The Yaksa flings questions at him, and Yudishtra’s replies show he could think clearly even in the midst of sorrow. Yaksa wants to know what makes the Sun rise, what makes it set, who accompanies it, and where the Sun remains grounded. The word used by the Yaksa is ‘Aditya,’ which means both sun and also jivatma.
Yudishtra’s answer is cleverly worded so that the full philosophical import of the question and of the answer becomes evident. He makes a clever use of the word ‘Brahma.’ He says Brahma makes the Sun rise. The story goes that the asuras did penance and asked Brahma to give them the power to conquer the Sun. Brahma gave them the boon they sought. When the celestials asked for a remedy, Brahma said the recital of the Gayatri mantra every morning would cause the Sun to rise. So Brahma may rightly be said to cause the rise and the setting of the Sun.
Gayatri mantra is used to make the Sun rise, and Gayatri mantra is also known as ‘Brahmam.’ So Yudishtra indicates this too by his choice of words. Brahma also indicates Parabrahma or the Supreme One. So Yudishtra is talking of the Supreme One here, as being responsible for the rising and setting of the Sun, which is, of course, indisputable, for everything is under the control of the Supreme One. This is indicated by the Vaishnavite Acharya Vedanta Desika. In his Abheeti Stavam in praise of Lord Ranganatha of Srirangam, Vedanta Desika says the Sun, Fire, Wind, Yama and Indra do their duties, out of fear of the Supreme One.
Yudishtra could just have answered simply that the Supreme One was responsible for making the Sun rise and set, and it would have been the absolute truth. So what was the need for a round-about answer? Yudishtra wanted his reply to be comprehensive and include every possible interpretation, while keeping the focus all the time on the Supreme One as the causative factor.