To Lakshmana, gifted with auspicious signs, Rama said "for the sake of killing one Rakshasa, you are not to kill all the Rakshasas on the earth". [6-80-38]
अयुध्यमानंप्रच्छन्नंप्राञ्जलिंशरणागतम् | पलायमानंमत्तंवा न हन्तुंत्वमिहार्हसि || ६-८०-३९
"You should not kill anyone who is not waging war, not fighting and hidden, one with folded palms surrendered, one who runs away from war and not alert in war." [6-80-39]