Albert Barnes Commentary 2 Kings 21:6

"And he made his son to pass through the fire, and practised augury, and used enchantments, and dealt with them that had familiar spirits, and with wizards: he wrought much evil in the sight of Jehovah, to provoke him to anger." — 2 Kings 21:6 (ASV)

For the meaning of the phrase “passing through the fire,” see 2 Kings 16:3 and Leviticus 20:2-5.

To “observe times” was forbidden in the Law and was undoubtedly one of the methods of divination practiced by the Canaanite nations. This has been explained in several ways:

1. Predicting from the state of the clouds and atmosphere.
2. Fascination with the eye.
3. Watching for and seizing upon chance words as omens.

Dealing with familiar spirits. This practice was forbidden by Moses in Leviticus 19:31 under the penalty of death (Leviticus 20:27). Its nature is best understood from Saul’s visit to the medium of Endor (1 Samuel 28:7 and following).

Wizards. The term “wizards,” literally meaning “wise men,” refers to those who are always associated with people who have familiar spirits. They were likely a type of necromancer.