Valmiki Ramayana Aranya Kanda Sarga 56 Shloka 1
Original Shlokaसा तथोक्ता तु वैदेही निर्भया शोककर्शिता। तृणमन्तरतः कृत्वा रावणं प्रत्यभाषत।।3.56.1।।
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तथा thus, उक्ता having addressed, शोककर्शिता sunk in deep sorrow, सा वैदेही that Sita, princess from Videha, निर्भया unafraid , तृणम् blade of grass, अन्तरतः between him and her, कृत्वा placed, रावणम् Ravana, प्रत्यभाषत replied.
Thus addressed by Ravana, Sita, immersed in deep sorrow and unafraid of him, placed a blade of grass between her and him (intending not to speak to him straight) and replied: Sita ridicules Ravana-- not willing to reply directly speaks to a blade of grass about Rama's might and Ravana's destruction-- Ravana sends Sita to Asoka garden.