Valmiki Ramayana Bala Kanda Sarga 37 Shloka 7
Original Shlokaइयमाकाशगा गङ्गा यस्यां पुत्रं हुताशन:। जनयिष्यति देवानां सेनापतिमरिन्दमम्।।1.37.7।।
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यस्याम् in this, हुताशन: fire god, अरिन्दमम् destroyer of enemies,, देवानाम् for devatas, सेनापतिम् army general, पुत्रम् son, जनयिष्यति will beget, इयम् such, आकाशगा flowing in the celestial regions, गङ्गा Ganga (exists).
"Ganga keeps flowing in the celestial regions. Through Ganga the Firegod will beget a son who will be capable of destroying enemies. He will become the army general of the gods".