KATHOPNISHAD CHAPTER 1 SHLOKA -21

               
                                                     देवैरत्रापि विचिकित्सितं पुरा
     
                                                      न हि सुविज्ञेयमणुरेष धर्मः ।

                                                      अन्यं वरं नचिकेतोवृणीष्व

                                                     मा मोपरोत्सीरति मा सृजैनम् ॥ २1
                                 
                                      DEVE ATRAPI VICHKITSITAM POORA

                                 NA HI SUVDHYEYAMANURESH DHARMH

                               ANYAM VARAM NACHIKETO VRUNISHWA

                                  MA MA UPAROTSI R MA SRUJAINAM ||21

EVEN THE GODS HAVE DOUBTS ON THIS (TOPIC) AS IT IS NOT EASY TO UNDERSTAND

                   BEING SUBTLE, OH NACHIKETA CHOOSE ANOTHER BOON,

                            DO NOT PRESS ME ON THIS, GIVE UP THIS ONE ||21

         This is a straight forward Shloka.
         Nachiket asked to know about life after death  and so it is a subject where many and most will not be interested or understand or appreciate . It will put most of us to sleep. So the Yama wants to make sure that the student is anxious enough to KNOW. Many of have questions , but we do not have ability or patients or time to really make efforts for the reaching higher levels. We all have seen this in our life. We attend spiritual lectures  and gave questions , but we do not work for it - practicing YAMA, NIYAMA, MEDITATIONS etc . We all want instant satisfaction. So Lord of Death wants to make sure that Nachiket , the mortal is READY for the discourse. Even in Ganapati Atharvshirsh,it is stated that Do not give this Stotra to wrong student.
       It is also possible that Yama wants to make sure that Nachiket HAS INTENSE DESIRE CALLED ART IN SANSKRIT, There is story . There was a teacher who had a student who was not following usual regular practices to achieve the highest levels of Samadhi. He was asking the teacher as when will he see the God . One day the teacher went to to a river for bathing  and doing morning prayers. The student accompanied him and had the same question. The teacher  and the student were in the waters . The teacher pressed the head of the student under water . The student started struggling  and the teacher continued to press it down . After short time , the teacher allowed him to get his head out of water  and breath. The student was surprised and asked teacher as to why did he do this. The teacher answered, "When his desire to see GOD would be as intense as was to breath under water , he will see God."