Molech was the chief god of the Ammonites (1 Kings 11:33), whom worshipers honored by sacrificing their own children (2 Kings 16:3; 21:6; Jeremiah 32:35). Jewish law (Leviticus 18:21; 20:1-5) and the prophets strictly forbade these kinds of heinous rituals. Zephaniah apparently regarded Molech worship as one of the most detestable form of Semitic idolatry (see Jeremiah 7:29-34; Ezekiel 16:20-22; 23:37-39; Amos 5:26).

ZEPHANIAH 1:5- And them that worship the host of heaven upon the housetops; and them that worship and that swear by the LORD, and that swear by Malcham;