Musannaf Ibn Abi Shayba 1:1505

Abu Bakr narrated to us, he said: Abu Usama narrated to us, from al-Walid ibn Kathir, from Muhammad ibn Ka’b, from Ubayd Allah ibn Abd al-Rahman ibn Rafi’ ibn Khadij, from Abu Sa’id al-Khudri: It was said, "O Messenger of Allah, shall one perform ablution from the well of Buda’ah?" He said—and it was a well into which menstrual rags, the flesh of dogs, and filth were thrown—the Messenger of Allah (peace and blessings of Allah be upon him) said, "Indeed, water is purifying; nothing makes it impure."