1 Kings 12:30-33

30And this thing became a sin; the people came to worship the one at Bethel and went as far as Dan to worship the other. Probable reading of the original Hebrew text; Masoretic Text people went to the one as far as Dan 31Jeroboam built shrines on high places and appointed priests from all sorts of people, even though they were not Levites. 32He instituted a festival on the fifteenth day of the eighth month, like the festival held in Judah, and offered sacrifices on the altar. This he did in Bethel, sacrificing to the calves he had made. And at Bethel he also installed priests at the high places he had made. 33On the fifteenth day of the eighth month, a month of his own choosing, he offered sacrifices on the altar he had built at Bethel. So he instituted the festival for the Israelites and went up to the altar to make offerings.