Why do we need Punishment under shariah law

The purpose of punishment under the Shari'ah is to discourage those who are not conscious of God's will from committing crime or vice (i.e. protection of innocent in this world).

Although ultimate justice is in the Hereafter, Islam is not only for peace in the Hereafter but also in this world. Lack of this balance gives rise to conflict (as in the West) between social order and individual freedom.

In any society, there is a maximum degree of crime and immorality it can reasonably tolerate. Shari'ah is to therefore protect the good, and not the bad. Society as a whole is more important than an individual criminal

Punishment is also to make evil/bad recognised as undesirable (e.g. punishment of children) just as reward is to teach desirable deeds.(it is one of known psychological method in learning) If it is fair to leave punishment to God, why do we reward the good? Sympathy in the West seems to be more with the criminal than with the victims, which leads to proliferation of crimes.

Punishment under Shari'ah is a command from Allah. Similarly in the Old Testament, the 10 Commandments of Moses and their respective legal punishments, e.g. Deuteronomy 22:22, which says that if a man is caught having intercourse with a married woman, both of them must die.

Every responsible parent punishes his or her child if it misbehaves or is disobedient.

Jesus himself found it necessary to inflict punishment on the moneychangers and animal-sellers in the Temple (John 2:13-16). He made a whip and drove them out of the Temple, and upset the tables of the moneychangers, accusing them of turning the place into a market.

The fact that he did not ignore them or leave them to God implies that the bad deserve punishment, as a correction of undesirable deeds.