Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.003A.

We can divide this category into two sub-categories:

1. The impure substance alters the taste, colour or odour of the water. In this case, it can not be used for purification. According to Ibn al-Munzhir and Ibn al-Mulaqqin, there is a consensus on this point.

2. The liquid is still considered water, meaning that the impure substance has not altered its taste, colour or odour. Such water is considered pure and may be used for purification. This is based upon the following hadith: Abu Hurairah reported that a bedouin urinated in the mosque. The people stood to get him (and stop him). The Prophet said, “Leave him and pour a bucket of water or a container of water over his urine. You have been raised to be easy on the people, not to be hard on them.” This hadith is narrated by “the group,” except for Muslim.

Abu Sa’eed al-Khudri asked the Prophet, “Can we make ablution from the well of Buda’ah (i.e., a well in Madinah)?” The Prophet, upon whom be peace, told him, “Water is pure and nothing makes it impure.”

This hadith is related by Ahmad, ash-Shaf’i, Abu Dawud, anNasa’i and at-Tirmizhi, who classified it as hassan. Ahmad said, “This hadith is sahih and Yahya ibn Ma’een and Muhammad ibn Hazm classified it as such.” This is also the opinion of Ibn ‘Abbas, Abu Hurairah, al-Hassan al-Basri, Ibn al-Musayyab, ‘Ikrimah, Ibn Abu Laila, al-Thauri, Dawud azh-Zhahiri, an-Nakha’i, Malik and others. Says al-Ghazzali, “I wish ash-Shaf’i’s opinion was like Malik’s.”

There is also a hadith from ‘Abdullah ibn ‘Umar in which the Messenger of Allah is reported to have said, “If there are at least two buckets of water, it will not carry any impurity.” This hadith is related by the “five.” However, this hadith is  muzhtarab in its chain of narrators and text. Ibn ‘Abdul-Barr said in at-Tamheed, “As to the opinion of ash-Shaf’i which is based on this hadith, it is weak on scrutiny and is not confirmed by historical reports.”