Shaykh Ibn 'Uthaymeen explains that 'tahara' (purification) in the Islamic legal context has a specific meaning beyond general cleanliness. While linguistically it means cleanliness and freedom from dirt, in the Shari'ah it refers to the removal of a state of ritual impurity (hadath) and the removal of physical, impure substances (najasah).

There are two types of tahara:

1. Abstract/Ritual Purification (tahara ma'nawiyyah): This is the purification from a state of 'hadath' (ritual impurity), which prevents a Muslim from performing certain acts of worship like Salah. 'Hadath' is not a physical substance but a state. Minor hadath (al-hadath al-asghar), caused by things like passing wind or using the toilet, is removed by performing Wudu (ablution). Major hadath (al-hadath al-akbar), caused by things like sexual relations or menstruation, is removed by performing Ghusl (a full ritual bath). If water is unavailable or its use is harmful, both can be removed by Tayammum (dry ablution).

2. Physical Purification (tahara hissiyyah): This refers to the removal of 'najasah'—impure substances as defined by the Shari'ah (e.g., urine, feces, blood, etc.)—from one's body, clothing, or the place where they intend to pray. This type of purification is achieved by washing the affected area with water until the substance is removed.

Therefore, to be in a state of 'tahara' for an act of worship like prayer, one must be free from both states of ritual impurity (hadath) and have removed any physical impurities (najasah) from their person, clothes, and place of prayer. This is a mandatory condition for the validity of Salah.