Most modern Christians do not believe that witchcraft genuinely works. Those Christians who do, generally believe that it derives its power from forces of evil. For example, some Christians believe that witches powers were obtained from a pact with Satan. Others take a slightly more moderate view that witchcraft is a false religion very little different from other religions they view as false. These, however, often believe that Satan will use his power to make the witch's spells appear to work in order to deceive people. The important difference here is that this view does not claim that witches actually consciously enter into a pact with Satan, which makes it somewhat more reasonable, in light of the fact that actual practicioners of Wicca do not believe in Satan.
With a few controversial exceptions such as Santeria, Christians do not practice witchcraft. Most Christians hold that Santeria, a syncretic hybrid of African animism and Christianity, is not Christianity at all. There are also various forms of mysticism which claim Christian roots, but most Christians do not see these as forms of Christianity either, and might call them forms of witchcraft or sorcery.
There are several references to witchcraft in the Christian Bible, and the strong condemnations of such practices which we read there do not seem to be based so much upon the supposition of fraud as upon the "abomination" of the magic in itself. (See Deuteronomy 18:11-12; Exodus 22:18, "wizards thou shalt not suffer to live" - A.V. "Thou shalt not suffer a witch to live".) The whole narrative of Saul's visit to the witch of En Dor (I Kings 28) implies the reality of the witch's evocation of the shade of Samuel; and from Leviticus 20:27: "A man or woman in whom there is a pythonical or divining spirit, dying let them die: they shall stone them: Their blood be upon them", we should naturally infer that the divining spirit was not a mere imposture.
The prohibitions of sorcery in the New Testament leave the same impression (Galatians 5:20, compared with Revelation 21:8; 22:15; and Acts 8:9; 13:6). Supposing that the belief in witchcraft were an idle superstition, it would be strange that the suggestion should nowhere be made that the evil of these practices only lay in the pretending to the possession of powers which did not really exist.
Many people today, particularly theologically conservative Christians, assume that these texts refer to any and all people to whom the word witch has been applied. In this view, anyone considered a "witch" is seen as condemned by the Bible.
Since the Middle Ages, Christians have used the term to refer to people who worshipped and consorted with Satan, the Devil, and/or other demonic forces. This usage was most famously applied in the Salem witch trials in colonial America. Some Christians still use the term in this medieval sense. The Malleus Maleficarum, a famous mediæval tract on witches, was often used as a source book for witch hunts.
Some claim that the use of this phrase in the Bible referred to a specific religious practice: some adherents of near-east religions acted as "mediums", channeling messages from the dead or from a "familiar spirit". The words "witch" and "witchcraft" in the Bible are sometimes translated "necromancer" and "necromancy" for this reason. However, some well-respected lexicographers, including James Strong and Spiros Zodhiates, disagree. These scholars say that the Hebrew word kashaph, used in Exodus 22:18 and 5 other places in the Tanakh comes from a root meaning "to whisper". Strong therefore concludes that the word means "to whisper a spell, i.e. to inchant or practise magic". The view that this word referred to mediums rather than witches or sorcerers as the words are used today is also refuted by the fact that the Hebrew word owb is used in the condemnation of mediums elsewhere. See Leviticus 20:27.
Whatever side one takes in the above controversy, one must acknowledge that interpreting "verses" in isolation is hermeneutically suspect. Verse divisions were added to the Bible in the middle ages, and the idea that verses were in any way units of meaning is a modern innovation.
The context of Exodus 22:18, as part of the laying forth of the Law of Moses makes it clear that its purpose to keep the religion of Yahweh's people distinct in its practices from those of the surrounding peoples. If an activity was part of the religion of a neighboring tribe, this in itself, rather than its own intrinsic evil, was sufficient to secure condemnation.
While a biblical "witch" has much in common with a modern spiritist, some argue that modern "witches" (usually practitioners of Wicca), are completely unrelated to the "witches" condemned in the Bible. It should be noted, however, that practitioners of Wicca do not accept the Bible as authoritative anyway. It should also be noted that Strong's definition of the word as including anyone who casts spells certainly includes those who practice Wicca.
Further discussion of people accused of being witches, and of those who claim to be witches, may be found in the articles witchcraft and witchhunt.
English Translations of Exodus 22:18