Isa 8:19-21
19 When men tell you to consult mediums and spiritists, who whisper and mutter, should not a people inquire of their God? Why consult the dead on behalf of the living?
20 To the law and to the testimony! If they do not speak according to this word, they have no light of dawn.
21 Distressed and hungry, they will roam through the land; when they are famished, they will become enraged and, looking upward, will curse their king and their God. (NIV)
What was the result of Saul preferring to consult others instead of inquiring of the lord directly?
1 Chr 10:13-14
13 Saul died because he was unfaithful to the LORD; he did not keep the word of the LORD and even consulted a medium for guidance,
14 and did not inquire of the LORD. So the LORD put him to death and turned the kingdom over to David son of Jesse. (NIV)
Deuteronomy
18
10 Let no one be found among you who sacrifices his
son or daughter in [1]
the fire, who practices divination or sorcery, interprets omens,
engages in witchcraft, 11 or casts spells, or who is a
medium or spiritist or who consults the dead. 12
Anyone who does these things is detestable to the LORD , and because
of these detestable practices the LORD your God will drive out those
nations before you. 13 You must be blameless before the
LORD your God.
The King James Version makes it clear that these are deadly abominations.
Deuteronomy 18
10 There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch.
11 Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer.
12 For all that do these things are an abomination unto the LORD: and because of these abominations the LORD thy God doth drive them out from before thee.
Regardless of these warnings, many today consult Mary, or other dead saints in prayer. Since this is an abomination, they need to be truly born again and obey the gospel.