1st - 5th Verse
Yama tells that two jivas in order to obtain the results of one's own actions performed in this world enters the cave of heart, the highest place of the supreme soul. People who are aware of the Brahma call them shadow and sunlight. They worship the five fold aspect of Lord Agni, the fire god. Shadow and sunlight here actually mean the Jivatma and the Paramatma. The Nachiketa fire is the bridge of all sacrificers who wish to get rid of unhappiness and attain the indestructible Brahman. It is a place where no fear exists. The embodied soul is as the rider, the body is the chariot, the intellect is the charioteer and the traveller is the Jiva or the Purusa. The sense organs are the horses and it travels the path of materialistic desires or things of interest. People who are learned call them as The Jiva that consists of the body, the mind and the sense organs. A person who does not have control over his sense organs and mind can never control the wild horses and tame them.
6th - 10th Verse
One who has complete control over his mind and the power to distinguish between the right and the wrong will have complete control over his sense organs. On the other hand one who does not possess intellect and has no control over his mind can never attain the Supreme Being. He would continue to wander in this world through further births. Thus, one full of knowledge and with a clean heart attains the Brahman and becomes immortal. A person who possesses intelligence like that of a rider and a controlled mind as the steering cord travels a long distance and finally becomes united with the Supreme Being.
11th - 17th Verse
Beyond the soul is the unmanifested, higher than the unmanifested is the soul i.e. Purasha. Nothing exits beyond the Purusha. It is the last limit and the highest goal. The Purusha remains hidden within all beings and all creatures. He cannot be seen but only the wise can realise him through their meditation. The intelligent man restrains the speech in his mind, the mind in the intellect, the intellect in the great soul, and the great soul in the Supreme Divine. Thus, one must try to attain the great teachers following whose words he would be able to attain the Supreme Being.