Valmiki Ramayana Sundara Kanda Sarga 37 Shloka 25
Original Shlokaकथयन्तीव चन्द्रेण सूर्येण च महार्चिषा। मत्पृष्ठमधिरुह्य त्वं तराकाशमहार्णवौ।।5.37.25।।
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त्वम् you, मत्पृष्ठम् my back, अधिरुह्य after climbing up, चन्द्रेण with the Moon, महार्चिषा flaming light, सूर्येण with the Sun, कथयन्तीव conversing, आकाशमहार्णवौ sky and ocean, तर cross.
"Climb on my back and cross the ocean through space in the flaming light, conversing with Moon and Sun.