Valmiki Ramayana Bala Kanda Sarga 35 Shloka 17

अथ thereafter, सर्वे सुरा: all devatas, देवतार्थचिकीर्षया desirous of fulfilling some purpose of devatas, त्रिपथगाम् flowing in three directions, नदीम् river, ज्येष्ठाम् eldest daughter, गङ्गां Ganga, शैलेन्द्रम् king of mountains, वरयामासु: proposed.

Thereupon all the devatas desirous of deriving some advantage proposed that the eldest daughter of the king of mountains, Ganga, flowing in three directions be given to them.