The World Federation One Stop Fiqh

Ruling 119

If a pure object touches an impure object and both or one of them is wet – such that the wetness of one transfers onto the other – the pure object also becomes impure; however, it does not become impure through multiple intermediaries [i.e. the spread of impurity is limited to two intermediaries].

An example: if the right hand has become impure (mutanajjis) with urine, and [after drying,] that hand touches the left hand with a new wetness, this touching causes the left hand to become impure; and if after drying, the left hand touches something else, such as some clothing, with a new wetness, the clothing also becomes impure; but, if the clothing touches some other object with a new wetness, that other object is not ruled to be impure. Therefore, the third intermediary [the clothing in the example above] is impure but it does not make anything impure. Furthermore, if the wetness is so little that it does not transfer onto another object, the pure object does not become impure even if it touches an intrinsic impurity.