He said to himself, "As things are now, if my people go to Jerusalem and offer sacrifices to the Lord in the Temple there, they will transfer their allegiance to King Rehoboam of Judah and will kill me."
After thinking it over, he made two bull-calves of gold and said to his people, "You have been going long enough to Jerusalem to worship. People of Israel, here are your gods who brought you out of Egypt!" 1
References for 1 Kings 12:28
12.28 Ex 32.4.
He placed one of the gold bull-calves in Bethel and the other in Dan.
And so the people sinned, going to worship in Bethel and in Dan.
References for 1 Kings 12:30
Jeroboam also built places of worship on hilltops, and he chose priests from families who were not of the tribe of Levi.
Jeroboam also instituted a religious festival on the fifteenth day of the eighth month, like the festival in Judah. On the altar in Bethel he offered sacrifices to the gold bull-calves he had made, and he placed there in Bethel the priests serving at the places of worship he had built. 2
References for 1 Kings 12:32
12.32, 33 Lv 23.33, 34.
And on the fifteenth day of the eighth month, the day that he himself had set, he went to Bethel and offered a sacrifice on the altar in celebration of the festival he had instituted for the people of Israel.