Charles Ellicott Commentary 2 Kings 17:28

"So one of the priests whom they had carried away from Samaria came and dwelt in Beth-el, and taught them how they should fear Jehovah." — 2 Kings 17:28 (ASV)

And taught. — And was teaching, implying a permanent work.

In Bethel. — Because he was a priest of the calf worship.

Fear the Lord. — Not in the modern ethical but in the ancient ceremonial sense.