Muhammad bin Ja'far bin Abi Kathir محمد بن جعفر بن أبي كثير · The Book of Purification

"The Messenger of Allah (ﷺ) was asked about water and how some animals and carnivorous beasts might drink from it. He said: 'If the water is more than two Qullahs, it will not carry filth.'" It comes with some explanation in Sunan At Timidhi 'Abdah (one of the narrators) said: "Muhammad bin Ishaq said: 'A Qullah refers to Jirar (These are two nouns describing large casks that are used to hold water), and a Qullah is the thing that drinking…