1 Kings 12:31-32

31Jeroboam also erected buildings at the pagan shrines and ordained priests from the common people—those who were not from the priestly tribe of Levi.

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.