1 Kings 12:30

Overview - 1 Kings 12
1	The Israelites, assembled at Shechem to crown Rehoboam, by Jeroboam make a suit of relaxation unto him.
6	Rehoboam, refusing the old men's counsel, answers them roughly.
16	Ten tribes revolting, kill Adoram, and make Rehoboam flee.
21	Rehoboam, raising an army, is forbidden by Shemaiah.
25	Jeroboam strengthens himself by cities;
26	and by the idolatry of the two calves.

1 Kings 12:30  (King James Version)
And this thing became a sin: for the people went to worship before the one, even unto Dan.