Valmiki Ramayana Yuddha Kanda Sarga 116 Shloka 47

लोकहिंसाविहाराणाम् who do cruel deeds in the world, रक्षसाम् Rakshasas, कामरूपिणाम् who assume form according their will, पापानि sinful, कुर्वतामपि even if they do sinful actions, अशोभम् sins, कार्यम् actions, न कार्यम् not to be done

"Rakshasas by nature are cruel in their deeds and can assume any form according to their will. No sinful actions to be done even if they do sinful actions."