“When people request revelation from sources not of God, such as the various forms of witchcraft enumerated in verse 19 … these sources are to be tested according to the law (of Moses) and the testimony (of the prophets). Elder Ezra Taft Benson quoted this scripture as a key for not being deceived and said that this great truth from Isaiah was so important that it was included in the Book of Mormon. … President Joseph Fielding Smith quoted verse 19 as an example of the Lord’s warning Israel not to seek after ‘familiar spirits’ or other ‘devices prevalent among the heathen nations’” (Nyman, Great Are the Words of Isaiah, 65–66).