Valmiki Ramayana Yuddha Kanda Sarga 19 Shloka 13
Original Shlokaसङ्ग्रामसमयव्यूहेतर्पयित्वाहुताशनम् । अन्तर्धानगतश्शत्रूनिन्द्रजिद् हन्तिराघव:।। 6.19.13।।
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राघव: Raghava, शत्रून् at enemies, इन्द्रजित् Indrajith, हुताशनम् god of fire, तर्पयित्वा: by satisfying, अन्तर्धानगतः goes unseen, सुमयव्यूहे: when caught by network of foes, सङ्ग्रामसमये: at the time of war, हन्ति: strikes.
"Raghava Indrajith strikes when caught by a network of foes in war by becoming invisible because of satisfying fire god."