Skandapurana 16.36.56

16.36.56

anyaddevi purā gītaṃ gāṃgeyena yudhiṣṭhire ..
satyameva hi gaṃgāyāṃ vayaṃ jātā yudhiṣṭhira .. 56 ..

Another thing, O Goddess, was sung of old by the son of Gaṅgā to Yudhiṣṭhira: / 'In truth, O Yudhiṣṭhira, we were born of the Gaṅgā;