“Sacrificed to Molech”
You must not give any of your children to be sacrificed to Molech, for you must not profane the name of your God. (Leviticus 18:21 BSB)
What it sounds like today
A ban on an obscure foreign ritual.
The cultural key
Molech (or Milcom) was a deity associated with the sacrifice of children by fire, a practice attested among Israel's Canaanite and Phoenician neighbors. The Law treats it as the ultimate abomination, and tragically Israel did fall into it, in the Valley of Hinnom (Topheth) just outside Jerusalem, under kings like Ahaz and Manasseh. That valley's name, Ge-Hinnom, passed into Greek as Gehenna, the New Testament word translated 'hell', so the place of Israel's most horrific sin became the very image of final judgment.
Recovered meaning
The one line Israel must never cross is the burning of its own children before a god. The valley where they crossed it anyway became so byword for horror that its name became the Bible's word for hell.