Valmiki Ramayana Yuddha Kanda Sarga 76 Shloka 54
Original Shlokaतमिन्द्रकेतुप्रतिमंवृक्षंमन्दरसन्निभम् ।।6.76.54।। समुत्सृजन्तंवेगेनपश्यतांसर्वरक्षसाम् ।
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सर्वरक्षसाम् all Rakshasas, पश्यताम् seeing, इन्द्रकेतुप्रतिमम् resembling Indra's banner, मन्दरसन्निभम् like the Mandara mountain, तंवृक्षम् that tree, वेगेन hurriedly, समुत्सृजन्तम् impatiently.
All the Rakshasas seeing the tall tree, which was like Mandara mountain, resembling Indra's banner hurriedly was about to let loose.