1 Kings 12:32-33

32Jeroboam appointed a festival on the fifteenth day of the eighth month, just like the festival in Judah. He went to the altar in Bethel to sacrifice to the calves he had made. He appointed priests from the illegal worship sites ⌞to serve⌟ in Bethel.

33He went to his altar in Bethel to burn an offering on the fifteenth day of the eighth month, ⌞the festival⌟ he had invented for the Israelites.