Valmiki Ramayana Ayodhya Kanda Sarga 12 Shloka 76
Original Shlokaसतीं त्वामहमत्यन्तं व्यवस्याम्यसतीं सतीम्। रूपिणीं विषसंयुक्तां पीत्वेव मदिरां नरः।।2.12.76।।
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रूपिणीम् beautiful, अत्यन्तम् extremely, असतीं सतीम् being an unchaste woman, त्वाम् you, नरः people, विषसंयुक्ताम् mixed with poison, मदिराम् wine, पीत्वेव having partaken, सतीम् like a chaste woman, व्यवस्यामि I have a sure belief.
Like people regarding wine mixed with poison as fine before drinking it, I had a firm belief that you were a chaste woman, but while you who look extremely beautiful you are actually not so.