The Malleus Maleficarum by Kramer and Sprenger, 1489, Excerpts
It is a most certain and most Catholic opinion that there are sorcerers and witches who by the help of the devil, on account of a compact which they have entered into with him, are able, since God allows this, to produce real and actual evils and harm, which does not render it unlikely that they can also bring about visionary and phantastical illusions by some extraordinary and peculiar means. Whether it be the casting of spells by a look or by a formula of words or by some other charm, it is all of the devil
There are wizards and sorcerers who by the power of the devil can produce real and extraordinary effects, and these effects are not imaginary, and God permits this to be. Sorcerers, and those too who are skilled in the art of divination, incur the penalty of death. It is unlawful for any man to practise divination; and if he does so his reward shall be death by the sword of the executioner.