"How can one know thus as to where It (the Self) is, for which both the brāhmaṇa and the kṣatriya become food, and for which Death takes the place of a curry?"

Namaste 🙏 So this is the close of the second chapter, the second Canto of this Upaniṣad, which has six Cantos in two parts. The first Canto was about setting the scene, creating a context where this wonderful conversation between death and Naciketā could take place. Naciketā is not going to take anything other than the highest knowledge. He doesn't want any material benediction.

So in the beginning of the second Canto, Death accepts Naciketā as his student and begins to teach him about Brahman. Because really, what Naciketā wants is to know Death's secret.