Leviticus 20:5
Then I will set my face against that man, and against his family, and will cut him off, and all that go a whoring after him, to commit whoredom with Molech, from among their people. Then I will set my face against that man, and against his family, and will cut him off, and all that go a whoring after him, to commit whoredom with Molech, from among their people.
The verse is part of the holy, civil law given to Israel when God directly ruled as king, set apart from the customs of the surrounding nations, and its prohibitions belong with laws governing unions forbidden by affinity, including incestuous unions. It is an example of the curses imposed for violating the covenant made with Israel in Moab, a covenant distinct from the one made at Horeb, showing that this law prescribed punishment for those who committed the prohibited acts. Whoredom with Molech means spiritual unfaithfulness and idolatry, which is treated as an abomination and shown to be serious by the severity of its consequences.
God himself will set his face against the offender and cut him off from among his people, and that judgment extends to his family and to all others who follow him in that worship. The verse belongs with the command for the people of the land to destroy worshipers of Molech, a destruction that probably took place in Gehenna where the image of Molech was placed, showing Gehenna was a place of punishment by burning. The death penalty attached to this and other commandments under the former dispensation was no part of the commandment itself but a subsequent enactment for that people in that place and time, the same as for Sabbath-breaking, so keeping the commandments now does not require stoning transgressors, and it is inconsistent to demand stoning for Sabbath-breaking while admitting the other commandments remain binding.
The Molech worship condemned was the pagan abomination of the nations around Israel, involving cruel, bloody rites and human sacrifice with Satan ruling through the flesh, and those human sacrifices were the scriptural justification for Israel's conquests. God in mercy gave those nations four hundred years of hope and sent his servants to sojourn among them to win them to the right way, but they filled up their cup of iniquity, so he cast them out of the Holy Land before Israel and blotted them from the earth as a blessing to future generations. Because the verse condemns Molech worship, offering Jephthah's daughter as a sacrifice would have violated God's law and could not properly be described as an offering to the Lord. The chapter's account of the evil such Canaanite practices produced and the divine judgment they brought warns by application of the danger of spiritualism in the last days.