Shaykh Ibn ‘Uthaymeen, in his detailed commentary on the Hanbali fiqh text 'Zad al-Mustaqni', explains the conditions (shuroot) that must be met for one's wudu (ablution) to be valid. These conditions are prerequisites that must be in place before and during the act of purification.

The conditions for a valid wudu are:

1. Islam: The person must be a Muslim. The good deeds of a disbeliever are not accepted until they embrace Islam.
2. Sanity ('Aql): The person must be of sound mind, as an insane person is not accountable.
3. Discernment (Tamyeez): The person must have reached the age of discernment, which is the ability to understand and intend the act of worship. This is typically around seven years of age.
4. Intention (An-Niyyah): One must have the specific intention to perform wudu for the purpose of purification or to make prayer permissible. This is a condition for the validity of all acts of worship.
5. Purity of the Water: The water used must be tahur—pure in itself and purifying for other things. Water that has been altered by a significant amount of an impure substance is not valid for wudu.
6. Permissibility of the Water: The water must be mubah (permissible). Using stolen water or water taken without permission is sinful, and wudu performed with it is not valid according to the Hanbali madhhab, a view Shaykh Ibn 'Uthaymeen explains in detail.
7. Removal of Barriers: One must remove anything from the limbs of wudu that would prevent water from reaching the skin, such as wax, thick paint, dough, or modern waterproof materials like nail polish.
8. Prior Cleansing (Istinja' or Istijmar): If one has relieved oneself, they must first cleanse the private parts from impurity before performing wudu.

Shaykh Ibn 'Uthaymeen also discusses two further points that are essential for the completion of wudu, which are often classified as pillars (arkan) or obligations (fara'id) but are functionally necessary for validity: continuity (al-muwalah), meaning not pausing for a long time between washing the limbs, and observing the correct order (at-tartib) as mentioned in the Qur'an.