In the name of Allah,
Scholars have disagreed in their classification of water, with the two strongest being:
There are three different kinds of water.
1- Purifying (tahur) – Pure (Tahir) – Impure (najis)
In general, the four schools of law have agreed to this. They differentiate on whether some forms of water are both pure and purifying.
2- There are only two kinds of water: purifying and impure. This is the viewpoint of some Hanafis, as well as Ibn Taymiyyah, Ibn Baz, and Ibn ‘Uthaymin, the old opinion of Imam Shafi[i], and Malikis.
Abu Sa‘eed al-Khudri (may Allah be pleased with him) said: It was said: O Messenger of Allah, can I do wudoo’ from the well of Budaa‘ah? It is a well into which are thrown menstrual rags, the flesh of dogs and other putrid things. The Messenger of Allah (blessings and peace of Allah be upon him) said: “Verily water is a means of purification and nothing makes it impure.” [ii]
The word used by the prophet in the hadith of Sa’eed al Khudri (R) is ’tahoor’ a superlative form of tahir. The scholars say that this term is used to refer both pure and purifying[iii].
Water, according to Ibn Taymiyah, is either impure or pure and cleansing. As long as it fits within the umbrella word of water, there is no third category of pure but not purifying.
Sheikh Nasir As Saadi said,’ The correct opinion is that water is of two types. 1 Pure and it purifies 2 impure and it makes things impure[iv].
”The Messenger of Allah (blessings and peace be upon him) wiped his head with the extra water that was in his hand.”[v]
This hadeeth is proof that used water is both pure and purifying.
Sources:
[i] The Evident Memorandum: A Translation and Commentary for Ibn al-Mulaqqin al-Shāfiʿī’s Al-Tadhkirah fi al-fiqh, Translated by Musa Furber, page 7
[ii] Narrated by Abu Dawood (66), at-Tirmidhi (66), and an-Nasaa’i (326); classed as saheeh by Imam Ahmad, Yahya ibn Na‘eem, at-Tirmidhi, an-Nawawi, Ibn Mulaqqin, and al-Haafiz Ibn Hajar. See: al-Majmoo‘ (1/82) and al-Badr al-Muneer (1/381)
[iii] Fiqh of Worship, Vol 1 Commentary on ‘Umdat al-Fiqh (The Reliable Source of Fiqh) Muwaffaq-ud-Deen, Abdullah ibn Ahmad ibn Muhammad ibn Qudamah al-Maqdisi, Commentary and translation by: Dr.Hatem al-Haj, page IIPH Publication, Page 39
[iv] Path of the Wayfarer, Sheikh Nasir As Sa’di, page 5
[v] Hasan (Al-Albani), Abu Dawood 130]