Islam has enacted capital punishments for certain crimes, but in order to establish and prove them, it has also laid down difficult conditions, thus making it very problematic to prove those crimes.
In dealing with the philosophy of divine laws, the considered wisdom behind punishments and penalties is the lesson taken from it which acts as a deterrent and thus prevents the spread of crimes and offenses. In order to reach this goal, there must be penalty commensurate with the crime and for heinous crimes capital punishment must be taken into account.
For example, if a light punishment—an insignificant fine or short-period detention—is taken into account for a criminal act like robbery, robbery in society will not stop and the hidden wisdom behind divine punishments and penalties will not be realized.
On the other hand, if it is easy to prove a crime and individuals can easily be punished, execution of punishments and penalties will spread in society because many deserve punishments, and thus the honor and reputation of many families will be tarnished.
It is for this reason that Islam has considered heavy punishment and even ordered that an unmarried fornicator should be banished for a year together with a hundred stripes on his / her body in order to serve as a deterrent for him and to prevent moral corruption in society. That is the reason why Islam has set difficult conditions for proving such a crime. As a result, very few cases of the crime are actually proven and only a few among the fornicators are punished.
The existence of such meticulousness and strictness in the implementation of all laws of Islam, the penal codes in particular, shows that Islam pursues the realization of its lofty goals and aspirations, observes sublime values, but insists on ground realities and is not contented with mere idealism. In fact, the method of Islam in administering society is between idealism and realism and contains elements of both. Islam considers it necessary to observe lofty values and does not allow them to be tarnished in society just as done in non-religious and non-Islamic societies that have brought about widespread corruption and ample ignominy.
From the aforementioned above, it is very glaring that the main aim and objective of Islam in the implementation of a year banishment of a fornicator is to prevent moral corruption in society whereby environment can also be a factor of corrupion. Hence banishment to a different environment better serves as a deterrent, exhortation for the fornicator and advise for others and prevents the spread of disorder and anarchism in the land.