Leviticus 20:6
And the soul that turneth after such as have familiar spirits, and after wizards, to go a whoring after them, I will even set my face against that soul, and will cut him off from among his people. And the soul that turneth after such as have familiar spirits, and after wizards, to go a whoring after them, I will even set my face against that soul, and will cut him off from among his people.
The law forbids turning after, seeking, or consulting those with familiar spirits and wizards, including mediums and all who claim contact with the dead, whether for guidance, communion, counsel, or to learn what God has veiled. The prohibition closes the way to any such pursuit, whatever form the claim of intercourse with the dead may take.
To turn to them is to go a whoring after them, which is spiritual unfaithfulness and adultery toward God, like breaking faith with a best and trusted friend. Those who do so are unfaithful to Him who should have their unfaltering trust.
By this law God sought to deliver Israel and separate His people from the abominations of the idolatrous nations around them. It shut the door to pretended communication with the dead, for the dead have no knowledge of or share in anything done under the sun, and their thoughts perish at death. Familiar spirits are spirits of devils, so intercourse with supposed spirits of the dead is in reality communion with devils. That intercourse defiles those who pursue it, exerts a corrupting and demoralizing influence, and gains only a knowledge of evil.
This turning springs from restlessness under uncertainty and impatience to tear away the veil from the future. It comes from unwillingness to wait for God's salvation, lack of unfaltering trust in God, and neglect of prayer and communion with God and of going to Jesus for divine consolation and rest of soul. God is displeased with this course and declares in explicit terms that He will set His face against that soul, oppose him, and cut him off and remove him from among His people.
The warning remains profitable today, for modern Spiritualism is a revival in new disguise of the witchcraft condemned by this law. We live in an age of peril and apostasy, when evil men grow worse and Satan works with deceivableness of unrighteousness, so no concession must be made to the enemy. The soul left open by distrust is led by Satan to mediums, who use knowledge of the past to inspire confidence and show extraordinary views of the future in order to bring the misguided soul into his power to lead captive at his will.