穆斯林法学家一致认为，法定的洁净（tahāra）分为两类：从小秽（ḥadath，即仪式不洁）中洁净，以及从大秽（khabath，即实体不洁）中洁净。他们还一致认为，从小秽中洁净分为三种：小净（wuḍū'）、大净（ghusl）以及二者的替代方式，即以洁净的土进行的干净土净（tayammum）。这是因为这三者都包含在涉及这些内容的小净经文之中。我们将从其中的小净开始讨论。我们说：

The Muslim jurists agreed that shai*i (legal) purity (tahdra) is of two types: purity from hadath (ritual impurity) and purity from khabath (physical impurity).23 24 They also agreed that purity from hadath is of three kinds: ablution (wudi?), bathing (gZws/), and their substitute, ablution with clean earth (tayammum)?* This is because of their inclusion in the verse of ablution,25 which dealt with these issues. We shall begin, out of these, with a discussion of ablution. We say: