Purity from impurities (najasah) in one's body, clothing, and place of prayer is a fundamental condition for the validity of Salah. It is not permissible for a Muslim to pray while knowingly having any impurity on their clothes if they are able to remove it by washing it or changing the garment.

Shaykh Ibn Baz clarified that if a person knows there is an impurity on their garment, no matter how small, their prayer is not valid if they perform it without removing the impurity first. This is because they have deliberately omitted one of the established conditions of prayer while having the ability to fulfil it. The ruling is different for one who prays while being unaware of the impurity, or who forgets about it and only remembers after the prayer is completed; in this case, their prayer is considered valid and they do not need to repeat it. Similarly, if someone is unable to find pure water to clean the garment or another pure garment to wear, they should pray as they are, and their prayer is valid.

However, for a person who is aware of the impurity and has the means to purify their clothing, it is obligatory to do so before beginning the prayer. To pray with it intentionally renders the prayer invalid.