If a Muslim wants his or her prayer, fasting or Hajj to be valid, then he or she must be in a state of ritual purity before performing those actions. In other words, one must be tāhir. To ritually purify oneself, one can do one of three things, perform wudū (minor ablution), ghusl (major ablution) or tayamum (purification through the use of earth or dust).

A common misunderstanding about tahāra and najāsa is equating the terms with cleanliness and dirtiness. But this is incorrect. Tahāra and najāsa refer to ritual purity and impurity, meaning that they are pure or impure within the context of religious rituals. For example, items that are

najis or ritually impure include pigs, dogs, blood, semen, or feces among many other things. But this does not mean they are necessarily dirty. A pig or a dog may be given a bath and thus be considered clean in the conventional sense but still ritually impure.

This distinction is really important to understand because often enough, it is used as a point to attack Islam. For example, a woman who is in her menses or who just gave birth will be required at some time to perform ghusl if she wants to pray again. But some people mistakenly interpret this as a form of sexism where they think that women's biology is dirty according to Islam. They forget that men can also enter states of ritual impurity, like when they discharge semen. So these kinds of ignorant statements should be discarded because 1) both genders have states of ritual impurity and 2) ritual impurity does not necessarily mean dirty!