Can sihr (witchcraft, magic) kill?

Yes, there is sihr that can kill. When discussing different forms of murder the scholars have mentioned that the person who kills another by means of a kind of sihr that usually kills should be executed (qisaas – retaliation), because he has killed by means of something that usually kills. Ibn Qudaamah said in al-Mughni (9/330): “The sixth kind: if he killed him by means of a kind of sihr that usually kills, then he has to be executed, because he has killed by means of something that usually kills, like killing by use of a knife. 

If he killed by means of something that does not usually kill or something that sometimes kills and sometimes does not, then he has to pay diyah (blood-money), but qisaas is not required, because he intended to do harm, and it is akin to beating someone with a stick (which may or may not kill).”

The ruling concerning the saahir (practitioner of sihr) in al-Mawsoo’ah al-Fiqhiyyah (24/267) says that in the case where he killed a person by means of his sihr… the majority say that killing by means of sihr may be done deliberately, in which case qisaas is required. According to the Maalikis, evidence or a confession is required. 

According to the Shaafi’is, if the person whom the practitioner of sihr killed was his equal , then qisaas is required if the killing was deliberate, which may be proven by a confession on the part of the saahir, such as his saying “I killed him by means of my sihr”, or “I killed him with this type of thing”, supported by the testimony of two reliable witnesses who have practised sihr in the past but have now repented, who can confirm that this kind of sihr usually kills. If it is a type that does not usually kill, then the matter is more akin to manslaughter.

Undoing the effects of magic on the groom on his wedding night

This is not necessarily the case, but it could happen. Some people are tested by means of someone else putting a magic spell on them which prevents them from having intercourse with their wives. Allaah says (interpretation of the meaning):

“And from these (angels) people learn that by which they cause separation between man and his wife, but they could not thus harm anyone except by Allaah’s Leave [al-Baqarah 2:102]

But if a person uses the prayers for refuge prescribed in Islam, Allaah will be sufficient for him against the evil of the magicians and others, and Allaah will take that (magic) away if it is present. So he has to read Aayat al-Kursi over himself, and al-Faatihah, and the verses which speak of sihr (magic), and “Qul Huwa Allaahu Ahad” and the Mi’wadhatayn, and it will go away by Allaah’s Leave. This has been tried a great deal. A good qaari’ (reader) from among the good and righteous people from whom one hopes for good may also recite for him. The reader may recite into water which the man may then drink from or wash with, and the harm will go away from him, or the reader may recite over him and blow onto him, and Allaah will cure him of that. All of these are means of keeping safe and sound.

Ruling on learning magic and removing spells from a person affected by magic

If that is by doing something permissible, such as reciting du’aa’s that are prescribed or permitted in Islam, or by using a ruqyah that is prescribed in Islam, there is nothing wrong with that. But if a person learns magic in order to counteract magic, or for any other purposes, then that is not permitted and in fact is something which nullifies a person’s Islam, because it is not possible to learn it without falling into shirk. That happens by worshipping the shayaateen (devils), by offering sacrifices to them and making vows to them, and other kinds of worship, and offering sacrifices to them and seeking to draw close to them with things that they love, until they serve a person and do what he wants. This is the mutual benefit which Allaah refers to in the aayah (interpretation of the meaning):

“And on the Day when He will gather them (all) together (and say): ‘O you assembly of jinn! Many did you mislead of men,’ and their Awliyaa’ (friends and helpers) amongst men will say: ‘Our Lord! We benefited one from the other, but now we have reached our appointed term which You did appoint for us.’ He will say: ‘The Fire be your dwelling place, you will dwell therein forever, except as Allaah may will. Certainly your Lord is All-Wise, All-Knowing.’”