Is water used for ablution or purification considered physically impure (najis)?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
The view held by Abu Yusuf, and one narration from Abu Hanifa, states that used water is physically impure (najis). This is based on the Prophet's command: 'No one should urinate in standing water, nor should anyone perform ghusl therein,' implying that washing therein is like urinating in it. They argue that purification (taharah) must originate from impurity, as purifying something already pure is nonsensical.
Supporting text
The counter-argument holds that the used water is pure. Evidence is the incident where companions nearly fought over the leftover water from the Prophet's wudu, and when the Prophet poured his wudu water on Jabir while he was sick. Furthermore, the Prophet and his companions used small vessels, meaning water splash from the user would inevitably fall back into the water, and if the used water were impure, it would have rendered the rest of the water impure. A narration states, 'Water does not become impure (yunjis)' when a woman stated she dipped her hand, while in a state of janabah, into the vessel the Prophet was using for wudu.