Ramayana
अथावसाने यज्ञस्य पूर्ववैरमनुस्मरन् । वसिष्ठरूपी राजानमिति होवाच राक्षसः ॥ 7-65-20 ॥
Then, at the conclusion of the sacrifice, a rakshasa, remembering an old enmity, took on the form of Vasishtha and spoke thus to the king.
english translation