Why has the Sharee'ah prescribed a corporal punishment for killing, Zina (adultery/fornication), and theft but not for dealing in Riba (interest), for example, although its harms affect the Islamic society as a whole? What should one do to purify himself from a major sin he has committed?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Allaah Almighty has prescribed corporal punishments as deterring measures against committing crimes that the human soul persistently urges to, such as Zina, sodomy, drinking alcohol, or crimes that result in the destruction of  religion, such as apostasy, or the corruption of the worldly life, such as Hirabah (highway murder or robbery using force and threats), slander and stealing. Riba is not included in the cases stated above. Moreover, many people reject it and avoid dealing with it for it involves doing wrong to others and consuming their money unjustly. Another reason for rejecting Riba is what people have experienced from its evils and harms on their lives in general and their economy in particular, even in some communist countries, Riba has been banned because of the harms it causes.

Furthermore, effects caused by Riba are not like those caused by apostasy, Hirabah, slander or theft. There is absolutely no doubt that the effects of those crimes are more dangerous and that their corruptions are even greater. For this reason, corporal punishments have been specifically prescribed for such types of crimes, apart from others. However, this should in no way mean that Riba is a minor sin; rather, it is a serious crime.

It is a fact that there is no specific corporal punishment for practicing Riba, however, it is to be punished by Ta‘zeer (discretionary punishment) since that is an established way of punishment for every sin for which there is no corporal punishment or specific expiation. Thus, the ruler can punish the one who deals in Riba in the way that he believes to be a deterrent for him and those who are like him from committing such a sin.

As for how a person can purify himself from a major sin that he has committed, the way to achieve this is to sincerely repent to Allaah Almighty, as He says (what means): {But whoever repents after his wrongdoing and reforms, indeed, Allaah will turn to him in forgiveness. Indeed, Allaah is Forgiving and Merciful.} [Quran 5: 39]

Allaah Knows best.