Hudud are a few fixed punishments in Islamic law for serious crimes such as theft, adultery, false accusation and robbery. They apply only when a very high standard of proof is met, and the Prophet ﷺ taught to avoid them wherever there is any doubt.
The fuller answer
For example, zina (adultery) needs four eyewitnesses to the act itself, or a voluntary and repeated confession, and the Quran prescribes a penalty for those who accuse without four witnesses. Theft requires that the stolen goods are above a certain value, taken from a safe place, with no hunger or necessity. In the famine in the time of 'Umar, he suspended the punishment for theft. The Prophet ﷺ turned away a man who confessed several times.
In reality, the hudud have been applied very rarely in history, and in the modern world most Muslim-majority countries do not apply them. Some scholars say they should be applied only in a society that provides justice and welfare first. The stoning punishment for adultery is based on the Sunnah and not on the text of the Quran, and scholars have disagreed about it. Critics see these penalties as harsh, and Muslims say their purpose is deterrence, with the strict conditions making conviction almost impossible.
[As for] the thief, the male and the female, amputate their hands in recompense for what they committed as a deterrent [punishment] from Allah. And Allah is Exalted in Might and Wise.
The [unmarried] woman or [unmarried] man found guilty of sexual intercourse - lash each one of them with a hundred lashes, and do not be taken by pity for them in the religion of Allah, if you should believe in Allah and the Last Day. And let a group of the believers witness their punishment.
And those who accuse chaste women and then do not produce four witnesses - lash them with eighty lashes and do not accept from them testimony ever after. And those are the defiantly disobedient,
This answer follows the mainstream Sunni understanding and is general learning, not a fatwa. Where Muslims differ, the answer says so. Have a question of your own? Write to us.