Charles Ellicott Commentary Leviticus 18:21

"And thou shalt not give any of thy seed to make them pass through [the fire] to Molech; neither shalt thou profane the name of thy God: I am Jehovah." — Leviticus 18:21 (ASV)

And you shall not let any of your seed. —Literally, And you shall not give any of your seed. Those who violate the sanctity of the marriage ties will readily sacrifice their children. Therefore, the prohibition to offer up their children to idols follows the law about unchastity.

Pass through the fire to Molech. —Literally, to let it pass to Molech, that is, to put the child into the hands of the figure of Molech, when it fell into the fire which was kindled in the hollow statue of this idol. Molech, also called Milcom, which denotes king, is described as the hideous idol, or the abomination of the Ammonites (1 Kings 11:5; 1 Kings 11:11).

The following graphic description has been handed down traditionally of this idol and its worship:—“Our sages of blessed memory say that while all other idols had temples in Jerusalem, Molech had his temple outside Jerusalem, in a place by itself. It was a brass and hollow image, bull-headed, with arms stretched out like a human being who opens his hands to receive something from his neighbor. Its temple had seven compartments, into which the offerers went according to their respective gifts.

If one offered a fowl, he went into the first compartment; if a sheep, into the second; if a lamb, into the third; if a ram, into the fourth; if a bullock, into the fifth; if an ox, into the sixth; and if he offered his son, he was conducted into the seventh compartment.

He first kissed the image, as it is written, let the sacrificers of men kiss the calf (Hosea 13:2), after which a fire was kindled in Molech until its arms became red hot; the child was then put into its hands, and drums were beaten to produce tremendous noises so as to prevent the shrieks of the child reaching the father’s ears, so that he would not be moved with pity towards his offspring.”

It was to this idol that Solomon erected a temple on the southern side of Mount Olivet (2 Kings 23:13). This idolatrous worship was punished with death by stoning .

Neither shall you profane. —Better, And you shall not profane, that is, by causing other nations to say that the Israelites regard their God as an inferior deity, and therefore offer to him animals, while to Molech they sacrifice their own children. Therefore, any act which is done in violation of his commands, or misrepresents God, or by which He is put on a par with other gods, is called “profaning the name of God” (Leviticus 20:3; Leviticus 21:6; Leviticus 22:2; Leviticus 22:32, and so forth).