My dear Vidura, of the two sons, Kaśyapa and Pūrṇimā, Pūrṇimā begot three children, namely Viraja, Viśvaga and Devakulyā. Of these three, Devakulyā was the water which washed the lotus feet of the Personality of Godhead and which later on transformed into the Ganges of the heavenly planets.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
पूर्णिमासूत विरजं विश्वगं च परन्तप । देवकुल्यां हरेः पादशौचाद्याभूत्सरिद्दिवः
pūrṇimāsūta virajaṃ viśvagaṃ ca parantapa | devakulyāṃ hareḥ pādaśaucādyābhūtsariddivaḥ
SB 4.1.14