1 Kings 12:31-33

31He made shrines on the high places, and made priests from every class of people, who were not of the sons of Levi.

32Jeroboam ordained a feast on the fifteenth day of the eighth month, like the feast that was in Judah, and offered sacrifices on the altar. So he did at Bethel, sacrificing to the calves that he had made. And at Bethel he installed the priests of the high places which he had made.

33So he made offerings on the altar which he had made at Bethel on the fifteenth day of the eighth month, in the month which he had devised in his own heart. And he ordained a feast for the children of Israel, and offered sacrifices on the altar and burned incense.