1 Kings 12:30-34

Now this thing became a sin, for the people went to worship before the one as far as Dan.

And he made houses on high places, and appointed priests from all the people who were not of the sons of Levi.

Jeroboam also instituted a feast in the eighth month on the fifteenth day of the month, like the feast that is in Judah, and he went up to the altar. So he did in Bethel, sacrificing to the calves which he had made. And he stationed in Bethel the priests of the high places which he had made.

Then he went up to the altar which he had made in Bethel on the fifteenth day in the eighth month, the month that he had devised in his own heart; and he instituted a feast for the sons of Israel and went up to the altar to burn incense.