If you were to define an obligatory act by saying, “It is that which has been commanded,” this would not be exclusive, because it includes other things as well—recommended acts would also fall under it. Thus, it does not distinguish it from other matters.

And if you were to say, “An obligatory act is that which Allah Most High has introduced with the words, ‘It is obligatory upon you,’” this too would be incorrect, because it does not encompass what is being defined. An act may be obligatory even if it is not expressed in this particular wording.

A ḥadd—which is the intended meaning here—also refers to a punishment prescribed by the Sacred Law for an act of disobedience, in order to prevent the commission of similar acts and to expiate the offender’s sin.

This final qualification is not essential, but it has been mentioned in order to make clear the wisdom behind the punishment. Its purpose is not punishment alone; rather, it has a wisdom: preventing the recurrence of similar acts, whether by the perpetrator himself or by others; and, secondly, expiating the offender’s sin.

For example, if a man commits unlawful sexual intercourse, he must be flogged one hundred lashes. This flogging is a punishment prescribed by Allah.

The wisdom behind it is:

First: deterrence, so that neither he nor anyone else commits it again.

Second: purification and expiation. If a person commits a sin and the prescribed punishment is carried out upon him, Allah expiates it for him; thus, Allah does not combine for him the punishment of this world and that of the Hereafter.