Of the two sons, Kasyapa & Purnima, Purnima begot three children, namely Viraja, Visvaga & Devakulya. Devakulya 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

Expressions researched:
"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-Bhagavatam

SB Canto 4

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.

SB 4.1.14, Translation and Purport

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.

Of the two sons Kaśyapa and Pūrṇimā, herein Pūrṇimā's descendants are described. An elaborate description of these descendants will be given in the Sixth Canto. It is also understood herein that Devakulyā is the presiding deity of the River Ganges, which comes down from the heavenly planets to this planet and is accepted to be sanctified because it touched the lotus feet of the Supreme Personality of Godhead, Hari.