1 Kings 12:32-33

32And Jeroboam instituted a religious festival in Bethel, held on the fifteenth day of the eighth month, in imitation of the annual Festival of Shelters in Judah. There at Bethel he himself offered sacrifices to the calves he had made, and he appointed priests for the pagan shrines he had made.

33So on the fifteenth day of the eighth month, a day that he himself had designated, Jeroboam offered sacrifices on the altar at Bethel. He instituted a religious festival for Israel, and he went up to the altar to burn incense.