KATHOPNISHAD CHAPTER 2 SHLOKA -19

                                                     हन्ता चेन्मन्यतेहन्तुँहतश्चेन्मन्यतेहतम् ।  

                                                   उभौतौ न विजानीतोनायँहन्ति न हन्यते ॥ १9

                                                   HANTA CHET MANYATE HANTU

                                                    HATAS CHET MANYATE HATAM |

                                                          UBHAU TAU N VIJANITO

                                                     NAYAM HANTI N HANYATE ||19

                  IF KILLER FEELS HE KILLED  AND THE VICTIM FEELS HE IS KILLED 

                     BOTH OF THEM DON'T KNOW THERE IS NO KILLER OR KILLED ||19

   This SHLOKA is similar to one that is in Bhagavat Geeta., where the Lord Krishna is making a statement which he states that the ATMAN is indestructible. It can not be altered by 5 Mahabhuta the 5 Great Elements. Does not get wet, does not get killed .burned etc So what we are told here by The Lord of Death that when some one is killed by someone, the killer can not say that he killed the person (Atman0 nor the killed is killed as people feel . This is due to the reasoning that the ATMAN can not be killed . So at time of death the ATMAN continues to pass from on body to another. So he is telling us that the DEATH does not kill Atman. If you remember that Nachiketa had asked a question to Lord Of Death as what happens at the time of death - some say he is there and some say he is gone. So Yama is answering the question 

    Just to refresh the concept of the human body , we have 3 bodies , the physical(external covering called STHULA SHARIR) and inner one ASTRAL or SUKSHMA SHARIR AND INNERMOST CALLED KARAN SHARIR or causal body . The Atman is limited to these bodies by ignorance. And so it is carried from one Physical Body to other with the same package of CAUSAL BODY AND ASTRAL BODY though the physical body has dies . The ATMAN is still there . But the ATMAN is not KILLED but continues . This is somewhat easy to understand but the statement that is made here is little difficult to understand , The Yama is telling that the ATMAN as such is NEVER killed even when the Causal Body or the Astral Body is not there . So we all know that Physical body decays  and we can see that . But since we don't see Causal Body and the Astral Body , one may think that they also don't die or ever destroyed .One may also think that Atman may be destroyed when these bodies are destroyed But the reality is that the ATMAN IS NEVER KILLED .