Musnad Abu Ya'la al-Mawsili 42:331

Abu Khaythama narrated to us, Yunus bin Muhammad narrated to us, Abd al-Aziz bin Muslim narrated to us, from Mutarrif, from Khalid bin Abi Nawf, from Sulayt, from the son of Abu Sa’id, from his father, who said: I reached the Messenger of Allah (may Allah bless him and grant him peace) while he was performing ablution from the well of Bada’ah. I said, "O Messenger of Allah, do you perform ablution from it while there is thrown into it what is thrown of filth?" He said, "Indeed, water is not made impure by anything."