Jamieson, Fausset and Brown on 2 Kings 21:6

6. made his son pass through the fire--(See on 2Ki 16:3).

observed times--from an observation of the clouds.

used enchantments--jugglery and spells.

dealt with familiar spirits--Septuagint, "ventriloquists," who pretended to ask counsel of a familiar spirit and gave the response received from him to others.

and wizards--wise or knowing ones, who pretended to reveal secrets, to recover things lost and hidden treasure, and to interpret dreams. A great influx of these impostors had, at various times, poured from Chaldea into the land of Israel to pursue their gainful occupations, especially during the reigns of the latter kings; and Manasseh was not only their liberal patron, but zealous to appear himself an adept in the arts. He raised them to be an influential class at his court, as they were in that of Assyria and Babylon, where nothing was done till they had ascertained the lucky hour and were promised a happy issue.