Valmiki Ramayana Sundara Kanda Sarga 30 Shloka 21

ततः then, मनस्विनी sensitive woman, विशालाक्षी largeeyed, माम् me, कामरूपिणम् who can change form at will, रावणम् to Ravana, जानमाना she may think, जातपरित्रासा frightened, शब्दम् sound, कुर्यात् may make.

By seeing me in this form, sensitive largeeyed Sita will scream loudly thinking that I am Ravana who can assume any form at his free will.