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; The host of heaven - Sun, moon, planets, and stars. This worship was one of the most ancient and the most common of all species of idolatry; and it had a greater semblance of reason to recommend it. See 2 Kings 23:6, 2 Kings 23:12; Jeremiah 19:13; Jeremiah 32:29.
That swear by the Lord, and that swear by Malcham - Associating the name of an idol with that of the Most High. For Malcham, see on Hosea 4:15 (note), and Amos 5:26 (note).