https://www.al-feqh.com/en/purification-of-water-in-islam" rel="nofollow - It is the purification of the heart from polytheism, sins etc. It is not possible to attain purification when the filth of polytheism lingers in the heart. As pointed out by Allah I:”O you who believe, verily, the mushrikun (polytheists, pagans, idolaters, disbelievers in oneness of Allah and in the message of Muhammad) are najas (impure). So let them not come near the Al-Masjid Al-Haram (the holy masjid in Makkah) after this year; and if you fear poverty, Allah I will enrich you, if He wills, out of His bounty. Surely, Allah is All-knowing, All-wise.” ( Tawbah:28)

And the Prophet ﷺ said: “Indeed the believer does not become impure.” [ agreed upon by Al-Bukhari and Muslim (This will be referred to as «agreed upon» in the remainder of the book).]

2-Physical Purification

It is the purification of the body from dirt and impurities. Physical purification entails two forms of purification:

1-Purification from Hadath (the state of ritual impurity)

Hadath is that which, when produced from or befalls a body, prevents a Muslim from acts of worship for which purification is a requisite, e.g. As-Salah (prayer), circumambulation of the Ka’abah etc. There are two types of Hadath:

Minor Hadath.. It is that which makes  https://www.al-feqh.com/en/wudu-ablution" rel="nofollow - ablution  imperative, like urine, defecation, passing wind and all other nullifiers of al-wudu’ (ablution). These will be listed later on in the text. Purification from these is achieved by performing al-wudu’. Allah I says: “O you who believe! When you intend to offer Salah (daily prayer), wash your faces and your hands (forearms) up to the elbows, rub (by passing wet hands over) your heads, and wash your feet up to the ankles. ”(Maidah:6)

Major Hadath .. It is that which makes ghusl (a purificatory bath) imperative, e.g. sexual relations, menstruation etc. Purification from this state is achieved by ghusl. Allah says: “If you are in a state of janabah (i.e. after sexual relations), purify yourselves (by bathing your whole body).” (Maidah:6)

If it is impossible to purify oneself through wudu or ghusl, then one purifies himself through Tayammum (a dry form of purification using soil, to be discussed in a later section).

2-Purification from Najasah (a physical impurity)

Removal of any physical impurity is obligatory, as Allah says: “And purify your garments”(Mudathir: 4).

And the Prophet ﷺ said; “Most of the punishment in the grave is a result of the lack of cleaning (oneself from) urine” [ narrated by Ibn Majah.] and “When any of you comes to the masjid (mosque), he should be mindful of his sandals. If he sees filth or dirt on one (of them), he should wipe it (off) and then (he can) pray in them.” [ narrated by Abu Dawud.]

Purification from physical impurities entails:

1-purification of the place of prayer

2-purification of clothes

3-purification of the body
source: https://www.al-feqh.com/en/purification-of-water-in-islam