Valmiki Ramayana Yuddha Kanda Sarga 19 Shloka 21
Original Shlokaअहत्वारावणंसङ् ख्येसपुत्रजनबान्धवम् । अयोध्यांनप्रवेक्ष्यामित्रिभिस्तैर्भ्रातृभिश्शपे ।।6.19.21।।
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सपुत्रजनबान्दवम् accompanied with sons and relatives and people, रावणम् Ravana, सङ् ख्ये: in war, अहत्वा: without putting an end to, अयोध्याम् into Ayodhya, नप्रवेक्ष्यामि: will not enter, तै: those, त्रिभिः three, भ्रातृभिः brothers, शपे vow.
"I vow upon my three brothers that I will not enter Ayodhya without putting an end to Ravana along with his people, sons and relatives."