Valmiki Ramayana Sundara Kanda Sarga 48 Shloka 37
Original Shlokaअवध्योऽयमिति ज्ञात्वा तमस्त्रेणास्त्रतत्त्ववित्। निजग्राह महाबाहुर्मारुतात्मजमिन्द्रजित्।।5.48.37।।
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अस्त्रतत्त्ववित् a knower of the secrets of all missiles, महाबाहुः strongarmed, इन्द्रजित् Indrajit, अयम् this, अवध्यः not be killed, इति this, ज्ञात्वा realising, तम् him, मारुतात्मजम् son of the Windgod, अस्त्रेण by the divine weaponBrahmastram, निजग्राह caught
Indrajit, the strongarmed hero, who knew the secrets of all missiles, realising that the son of the Windgod cannot be killed caught him by the divine weapon of Brahma (Brahmastram).