Valmiki Ramayana Yuddha Kanda Sarga 73 Shloka 29
Original Shlokaस पावकंपावकदीप्ततेजाहुत्वामहेन्द्रप्रतिमप्रभावः । स चापबाणासिरथाश्वसूतःखेऽन्तर्दधेऽत्मानमचिन्त्यरूपः ।।6.73.29।।
1 source checked for this shloka
पावकदीप्ततेजाः flaming like fire god, महेन्द्रप्रतिमप्रभावः endowed with the prowess of Indra, अचिन्त्यरूपः of inconceivable form, सः he, सचापबाणासिरथाश्वसूतः with bow, arrows and chariot, खे into the sky, आत्मानम् himself, अन्तर्दधे disappeared.
Flaming like fire god, endowed with the prowess of Indra, possessing inconceivable form, Indrajith with his bow, arrows and chariot disappeared into the sky.