|Chapter 2: Contents of the Gita Summarized|
jatasya hi dhruvo mrityur
dhruvam janma mritasya ca
tasmad apariharye 'rthe
na tvam socitum arhasi
One who has taken his birth is sure to die, and after death one is sure to take birth again. Therefore, in the unavoidable discharge of your duty, you should not lament.
Krishna makes two important points here. First that death is inevitable for all who have taken birth. Simply because of past and present karmic reactions, the soul is forced to accept a material body. Birth and death happens when the eternal soul makes and breaks contact with the material body. By not fighting, Arjuna cannot stop this inevitable cycle of birth and death. This point is again explained in the next verse (2.28). Just in case people use this as an excuse for indiscriminate killing, Krishna clarifies that this is only permitted in the "unavoidable discharge of your duty." So only if by the prescribed duty one is expected to kill, then and only then it is sanctified otherwise not. Earlier on (1.43-1.45) Arjuna had objected to fighting on grounds that he could incur the sinful reactions of killing his guru and elders. Krishna now tells him that he would actually incur sinful reaction by not killing them, for in doing so he would neglect his prescribed duty as a king and ksatriya. In this way Krishna dismantles another of Arjuna�s objection.
Please read the Sanskrit Verse and the Prabhupada's Purport.