1 Kings 12:32-33

32He decided to have a festival on the 15th day of the eighth month each year. He wanted it to be like the festival that they had in Judah. He offered sacrifices on the altar in Bethel to the gold cows that he had made. He also chose priests to serve at the places that he built for people to worship.

33On the 15th day of the eighth month, Jeroboam offered sacrifices on the altar that he had made at Bethel. That was the special day that he himself had decided to choose as a festival for the Israelites. On that day, he burned incense on the altar.