Ramayana
ततः सा राक्षसी गर्भं घनगर्भसमप्रभम् । प्रसूता मन्दरं गत्वा गङ्गा गर्भमिवाग्निजम् ॥ 7-4-24 ॥
Then that rakshasi, having gone to Mount Mandara, brought forth the embryo, radiant as the heart of a thundercloud, as the Ganga brought forth the embryo born of Agni (Skanda).
english translation