Bhagavad Gita Chapter 2.27
jātasya hi dhruvo mṛtyur
dhruvaḿ janma mṛtasya ca
tasmād aparihārye ‘rthe
na tvaḿ śocitum arhasi
Translation
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.