| Clarke's Commentary on the Bible A familiar spirit - A spirit or demon, which, by magical rites, is supposed to be bound to appear at the call of his employer. See the notes on Genesis 41:8; Exodus 7:11 (note), Exodus 7:22 (note), Exodus 7:25 (note); and Leviticus 19:31 (note). From the accounts we have of the abominations both of Egypt and Canaan, we may blush for human nature; for wherever it is without cultivation, and without the revelation of God, it is every thing that is vile in principle and detestable in practice. Nor would any part of the habitable globe materially differ from Egypt and Canaan, had they not that rule of righteousness, the revealed Law of God, and had not life and immortality been brought to light by the Gospel among them. From these accounts, for which we could easily find parallels in ancient Greece and Italy, we may see the absolute need of a Divine revelation, without which man, even in his best estate, differs little from the brute.
Gill's Exposition of the Entire BibleA man also or a woman that hath a familiar spirit,.... Or the spirit of Python or divination, see Leviticus 19:31; such as the damsel had in Acts 16:16; a woman is here particularly mentioned, though before included in the above law; because, as Aben Ezra says, such sort of practices were more frequently committed by women; to which Maimonides (l) adds another reason, because men have a natural clemency towards the female sex, and are not easily prevailed upon to put them to death; therefore the law says, "thou shall not suffer a witch to live", Exodus 22:18, or that is a wizard; a knowing one, who pretends to a great deal of knowledge of things; as of lost or stolen goods, and even knowledge of things future, and imposes upon persons, and cheats them of their money they give for information: such shall surely be put to death: and not spared through favour and affection: the death they are to be put to follows: they shall stone them with stones; until they are dead; of the manner of stoning; see Gill on Acts 7:58, their blood shall be upon them: they are worthy of death, and they shall suffer it: this phrase following upon the former, the Jews (m) gather from hence, that, wherever it is used, it is to be understood of stoning; See Gill on Leviticus 20:9. (l) Moreh Nevochim, par. 3. c. 37. (m) Torat Cohanim in Yalcut in loc.
Keil and Delitzsch Biblical Commentary on the Old TestamentBut because Israel was called to be the holy nation of Jehovah, every one, ether man or woman, in whom there was a heathenish spirit of soothsaying, was to be put to death, viz., stoned (cf. Leviticus 19:31), to prevent defilement by idolatrous abominations.
Geneva Study BibleA man also or woman that hath a familiar spirit, or that is a wizard, shall surely be put to death: they shall stone them with stones: their blood shall be upon them.
Wesley's Notes 20:27 A man or a woman that hath a familiar spirit, shall surely be put to death - They that are in league with the devil, have in effect made a covenant with death: and so shall their doom be.
Matthew Henry's Concise Commentary20:10-27 These verses repeat what had been said before, but it was needful there should be line upon line. What praises we owe to God that he has taught the evil of sin, and the sure way of deliverance from it! May we have grace to adorn the doctrine of God our Saviour in all things; may we have no fellowship with unfruitful works of darkness, but reprove them. | 
