Deuteronomy 18:20
But the prophet, which shall presume to speak a word in my name, which I have not commanded him to speak, or that shall speak in the name of other gods, even that prophet shall die. But the prophet, which shall presume to speak a word in my name, which I have not commanded him to speak, or that shall speak in the name of other gods, even that prophet shall die.
A prophet who dares to speak in God's name what He has not commanded, or who speaks in the name of other gods, is guilty of a capital offense and must die. The command stands among warnings against familiar spirits, necromancy, enchantment and other heathen witchcraft, which rest on the false belief that the dead are conscious and are forbidden as a mercy to keep people from deception and ruin. The chapter thus gives the rule for detecting false prophets, for no claim to speak in the Lord's name is to be accepted when it sets aside His law or promises life to the transgressor, even if accompanied by signs and wonders. The promise of the prophet like Moses in verses 15-18 foretells the coming of Jesus Christ, in whom the instruction about the true prophet and the judgment of false prophets finds its fulfillment.
Context and Plain Meaning
Deuteronomy 18 belongs to instruction that condemns dealings with familiar spirits and other forms of witchcraft, exposing those practices as false and dangerous. The prohibition is merciful, warning people away from deception and ruin. Witchcraft and related practices were widespread among the nations God drove out before Israel. They rested on the belief that the dead remain conscious, with necromancy seeking knowledge through the dead, enchantment making unreal things appear real, and familiar spirits claiming to offer communion with the dead.
Familiar spirits are wicked and deceitful, so their claims about who they are cannot be trusted. The nations in Canaan committed abominations, including profaning the name of God, and the Lord drove them out from before Israel because of these abominations. Since guilt for violating the command against profaning God's name was imputed to them, that law was already in force and known to them, even though Genesis gives no record of its giving. Observing times is expressly forbidden and designated as a heathen practice, not anything required by the true God.
For this reason the observing of days and months and times and years rebuked by Paul cannot refer to keeping the Sabbath commanded by the Creator, but to heathen observances connected with gods which by nature are no gods. The verse itself declares that a prophet who presumptuously speaks in God's name what He has not commanded is guilty of a capital offense and shall die. The same judgment falls on one who speaks in the name of other gods, who is likewise subject to death. The execution of Baal's prophets carried out this command against those who spoke for another god.
Test, Prophecy, and Application
Deuteronomy 18 gives Bible rules by which false prophets may be detected and true prophets decided, and this verse is the test within that chapter. The chapter containing that test also contains a direct prophecy of Christ. The law of God is the test of a prophet, so one who speaks against God's law or leads people away from it is false, even when performing signs and wonders. A claim to speak in the Lord's name must not be accepted when it makes void one of God's commandments or promises life to one who transgresses, and such teaching is to be opposed in the Lord's name. A prophet who presumptuously speaks in God's name what He has not commanded, or who speaks in the name of other gods, is guilty of a capital offense and shall die, and the execution of Baal's prophets carried out this command against those who spoke for another god.
The verse has been invoked to condemn teaching the seventh-day Sabbath without divine direction, a charge answered by challenging as unproved the claim that the Holy Spirit did not guide anyone to Sabbath observance. The verse stands within instruction on prophecy in which verses 15-18 foretell the coming of Jesus Christ. The passage of 18:15-22 about the prophet like Moses and the judgment of false prophets is fulfilled in Jesus Christ alone.
The verse has been included in the claim that the prophet Moses foretold is one and the same person as the Messenger of the Covenant and Elijah the Restorer, an identification presented as requiring proof from Scripture.