"The Blessed Lord said: While speaking learned words, you are mourning for what is not worthy of grief. Those who are wise lament neither for the living nor the dead." BG 2.11
http://www.krishnapath.org/free-ebooks-audiobooks-of-srila-prabhupada/bhagavad-gita-as-it-is-original-1972-macmillan-edition/
