Ezekiel 16:20,21

“Moreover you have taken your sons and your daughters, whom you have borne to me, and these you have sacrificed to them to be devoured. Were your whoredoms a small matter that you have slain my children, and delivered them up, making them pass through the fire to them?”

To all that had gone before they had added this, that their own children whom they had borne to Yahweh, for all the firstborn were especially His, they had passed through the fire to Molech, to be devoured by him in the fire. Were their previous sins of unfaithfulness of such light importance that they could add this gross sin? Note the ‘my children'. They had slain those who belonged to Yahweh by offering them to other gods. Thus they had added theft, murder and sacrilege to their other sins.

Child sacrifice had been long known in Canaan, usually, but not always, to Molech, (Leviticus 18:21; Leviticus 20:2; Deuteronomy 18:10; 2 Kings 23:10; Psalms 106:38). That was why God had given the important lesson to Abraham that it was not by slaying his son that he would please God (Genesis 22). He learned the lesson that, in the words of Micah, ‘shall I give my firstborn for my transgression, the fruit of my body for the sin of my soul? He has shown you, O man, what is good. And what does Yahweh require of you, but to do justly, and to love mercy and to walk humbly with your God?' (Micah 6:6). But it seems to have increased dramatically around the period just prior to that in which Ezekiel is speaking (Jeremiah 7:31; Jeremiah 32:35).