From the Conquest of Death, in the Upanishads:

Chapter One explains how Nachiketas, after having been sacrificed by his father Vajasravasa to Yama - whom the footnote calls "The King of Death"- wins three boons, or wishes, due to the King's inhospitable reception.

Chapter Two discusses the wishes.

Nachiketas said: 'O Death, as the first of the three boons I choose that Gautama, my father, be pacified, kind, and free from anger towards me; and that he may know me and greet me, when I shall have been dismissed by thee."

Yama grants this wish.

Nachiketas said: 'In the heaven-world there is no fear; thou art not there, O Death, and no one is afraid on account of old age. Leaving behind both hunger and thirst, and out of the reach of sorrow, all rejoice in the world of heaven.
'Thou knowest, O Death, the fire-sacrifice which leads us to heaven; tell it to me, for I am full of faith. Those who live in the heaven-world reach immortality--this I ask as my second boon.'
Yama said: 'I tell it thee, learn it from me, and when thou understandest that fire-sacrifice which leads to heaven, know, O Nachiketas, that it is the attainment of the endless worlds, and their firm support, hidden in darkness.'
...
The generous, being satisfied, said to him: 'I give thee now another boon; that fire-sacrifice shall be named after thee, take also this many-coloured chain.
'He who has three times performed this Nachiketa rite, and has been united with the three (father, mother, and teacher), and has performed the three duties (study, sacrifice, almsgiving) overcomes birth and death. When he has learnt and understood this fire, which knows (or makes us know) all that is born of Brahman, which is venerable and divine, then he obtains everlasting peace.
'He who knows the three Nachiketa fires, and knowing the three, piles up the Nachiketa sacrifice, he, having first thrown off the chains of death, rejoices in the world of heaven, beyond the reach of grief.
'This, O Nachiketas, is thy fire which leads to heaven, and which thou hast chosen as thy second boon. That fire all men will proclaim. Choose now, O Nachiketas, thy third boon.'
Nachiketas said: 'There is that doubt, when a man is dead--some saying, he is; others, he is not. This I should like to know, taught by thee; this is the third of my boons.'
Death said: 'On this point even the gods have doubted formerly; it is not easy to understand. That subject is subtle. Choose another boon, O Nachiketas, do not press me, and let me off that boon.'
Nachiketas said: 'On this point even the gods have doubted indeed, and thou, Death, hast declared it to be not easy to understand, and another teacher like thee is not to be found--surely no other boon is like unto this.'
Death offers many temptations to be let off that boon.
Nachiketas said: 'these things last till to-morrow, O Death, for they wear out the vigour of all the senses. Even the whole of life is short. Keep thou thy horses, keep dance and song for thyself.
'No man can be made happy by wealth. Shall we possess wealth, when we see thee? Shall we live, as long as thou rulest? Only that boon which I have chosen is to be chosen by me.
'What mortal, slowly decaying here below, and knowing after having approached them, the freedom from decay enjoyed by the immortals, would delight in a long life, after he has pondered on the pleasures which arise from beauty and love?
'No, that on which there is this doubt, O Death, tell us what there is in that great hereafter. Nachiketas does not choose another boon but that which enters into the hidden world.'

From The Wisdom of India and China, edited by Lin Yutang (this may be it). I'm pretty sure the copyright has expired.

More later.