What is the punishment for an immature (one who is not reached puberty) boy or girl who commits rape, murder or robbery? For example, what is the punishment for a nine-year-old boy or girl who commits robbery, murder or rape?

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 is His slave and Messenger.

A person who has not yet reached the age of puberty is not held accountable for his deeds because reaching the age of puberty is a condition for one being held accountable for his deeds. Ali ibn Abi Taalib narrated that the Prophet said, “The pen is lifted (stopped from writing the deeds) from three kinds of people: the mentally-handicapped or insane person till he becomes able to reason, the sleeping person until he wakes up, and the child till he grows up (reaches the age of puberty).” [Abu Daawood - saheeh (sound)]

Therefore, there is no punishment in the Hereafter for a child below the age of puberty if he did some of the evil deeds that you mentioned in the question, and there is no hadd (i.e. the corporal punishment determined by the Islamic Law) to be applied on him in this worldly life if he commits any sin that necessitates a hadd.

However, if his deed involved what necessities dhamaan (guarantee), then he is liable, because liability for damages is included in khitaab al-wadh'a (i.e. the address related to the action of the servants in terms of declaration, like making of a thing a cause [sabab] or preventative factor [maani’] etc. Hence, such a thing is just a sign for the ruling. For example, the moving of the sun from its zenith is a cause for performing the thuhr prayer being obligatory but not a request to perform it, and the impurity invalidating is a preventative factor from the validity of the prayer but not a request to abstain from impurity. Similarly, damaging an item is a cause of the liability for damages regardless of whether the one who caused the damage is mature or not); so this guarantee [liability] includes the person who has reached the age of puberty and the one who is below the age of puberty and the one who is at fault and the one who is not.

Ad-Dardeer said in his commentary on Mukhtasar Khaleel, from the Maaliki School, “The child bears liability from his own money for what he has damaged if he has any money, otherwise the price remains a liability that he is obliged to repay when he grows up and becomes able; this is the correct opinion...”

Therefore, the child guarantees to pay stolen money and the indemnity for deflowering the virginity of a girl in case of rape, and his family guarantees to pay the diyah (blood money), even in case of a deliberate murder.

Allaah knows best.