Mbh 9.44.2a

Vaishampayana said, "This curiosity that thou feelest is worthy of thy birth in Kuru's race. The words that I shall speak, will, O Janamejaya, be conducive to thy pleasure. I shall narrate to thee the story of the investiture of Kumara and the prowess of that high-souled one, since, O ruler of men thou wishest to hear it! In days of yore the vital seed of Maheshvara coming out, fell into a blazing fire. The consumer of everything, the adorable Agni, could not burn that indestructible seed. On the other hand, the bearer of sacrificial libations, in consequence of that seed, became possessed of great energy and splendour. He could not bear within himself that seed of mighty energy. At the command of Brahman, the lord Agni, approaching (the river) Ganga, threw into her that divine seed possessed of the effulgence of the Sun. Ganga also, unable to hold it, cast it on the beautiful breast of Himavat that is worshipped by the celestials. Thereupon Agni's son began to grow there, overwhelming all the worlds by his energy. Meanwhile (the six) Krittikas beheld that child of fiery splendour. Seeing that puissant lord, that high-souled son of Agni, lying on a clump of heath, all the six Krittikas, who were desirous of a son, cried aloud, saying, 'This child is mine, this child is mine!' Understanding the state of mind of those six mothers, the adorable lord Skanda sucked the breasts of all having assumed six mouths. Beholding that puissance of the child, the Krittikas, those goddesses of beautiful forms, became filled with wonder. And since the adorable child had been cast by the river Ganga upon the summit of Himavat, that mountain looked beautiful, having, O delighter of the Kurus, been transformed into gold! With that growing child the whole Earth became beautiful, and it was for this reason that mountains (from that time) came to be producers of gold. Possessed of great energy, the child came to be called by the name of Kartikeya.