Valmiki Ramayana Aranya Kanda Sarga 46 Shloka 36
Original Shlokaनिमन्त्र्यमाणः प्रतिपूर्णभाषिणीं नरेन्द्रपत्नीं प्रसमीक्ष्य मैथिलीम्। प्रसह्य तस्याहरणे धृतं मनः समर्पयत्स्वात्मवधाय रावणः।।3.46.36।।
1 source checked for this shloka
निमन्त्र्यमाणः as he was being invited, रावणः Ravana, प्रतिपूर्णभाषिणीम् softspoken, नरेन्द्रपत्नीम् wife of the king, मैथिलीम् Maithili, प्रसमीक्ष्य looking at her, स्वात्मवधाय for his own destruction, प्रसह्य forcibly, तस्याः her, हरणे to abduct, मनः set his mind, धृतम् intent upon, समर्पयत् presented.
Ravana was observing the princess from Mithila, wife of a king inviting him and speaking to him in cordial manner. Looking at her, he resolved to abduct her forcibly, inviting his own death.