1 Kings 12:32-33

32 He instituted a festival on the fifteenth day of the eighth month, like the festival held in Judah, and offered sacrifices on the altar. This he did in Bethel, sacrificing to the calves he had made. And at Bethel he also installed priests at the high places he had made.
33 On the fifteenth day of the eighth month, a month of his own choosing, he offered sacrifices on the altar he had built at Bethel. So he instituted the festival for the Israelites and went up to the altar to make offerings.
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