al-Walid bin Kathir al-Makhzumi الوليد بن كثير المخزومي · The Book of Water

"I passed by the Prophet (ﷺ) when he was performing Wudu' from the well of Buda'ah. I said: 'Are you performing Wudu' from it when garbage is thrown into it?' He said: 'Water is not made impure by anything.'"