Valmiki Ramayana Bala Kanda Sarga 43 Shloka 25

शङ्करशिरोभ्रष्टम् descended on the Shankara's head, पुन: again, भूमितले on the earth, भ्रष्टम् fallen, गतकल्मषम् freed from impurities, निर्मलम् pure, तत् तोयम् those waters, तदा then, व्यरोचत looked splendid.

The waters of Ganga descended on Shankara's head and from there to the earth. Freed from all impurities, the waters looked pure and clean.