The ‘Illah is the Baa’ith (reason, motive) for the legislation whilst the Sabab is that which notifies of the presence of the Hukm within the reality. It (the Sabab) is not related to the legislation of the Hukm in order to treat the reality.

Example:

Allah Ta’Aalaa said:

The decline of the sun is the Sabab for the presence of the Zhohr prayer and the ‘Dulook’ of the sun is when it declines from the centre of the sky as a sign to identify the presence of Salaat uzh-Zhohr.

This is whilst the ‘Illah is the reason or motive for the legislation of the Hukm and it is not a Sabab (cause) for its existence (in the reality). For example, the Sabab for the existence of Salaat ul-Jumu’ah is the decline of the sun from the centre of the sky whilst ‘Al-Ilhaa’’ (distraction) is the ‘Illah for the prohibition of conducting trade at the time of the Salaah.

Consequently, the Sabab brought Jumu’ah prayer into being. As for the ‘Illah then it brought the Hukm that is related to the prayer into being.

From amongst the definitions of ‘As-Sabab’ is the following:

It is that which necessitates from its existence the existence (of the Hukm) and necessitates through its absence the absence (of the Hukm). Consequently, if the Zawaal (decline of the sun from the meridian) has taken place then the Hukm has taken place (i.e. come into being) and if it hasn’t occurred then the (obligation of the)

Salaah has not occurred.