Valmiki Ramayana Aranya Kanda Sarga 29 Shloka 16
Original Shlokaप्राकृतान्राक्षसान्हत्वा युद्धे दशरथात्मज। आत्मना कथमात्मानमप्रशस्यं प्रशंससि।।3.29.16।।
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दशरथात्मज O Rama, son of Dasaratha, युद्धे in war, प्राकृतान् ordinary ( people), राक्षसान् demons, हत्वा killing, अप्रशस्यम् not praiseworthy, आत्मानम् yourself, आत्मना by yourself, कथम् why, प्रशंससि praising.
O son of Dasaratha, it is not praiseworthy to kill ordinary demons in war. Why do you praise yourself for it?