And this thing became a sin; the people walked as far as Dan to worship before one of the calves.
We have here the beginning of the reign of Jeroboam. He built Shechem first and then Penuel - beautified and fortified them, and probably had a palace in each of them for himself (Kg1 12:25), the former in Ephraim, the latter in Gad, on the other side Jordan.
Commenting on 1 Kings 12:25-33
And Jeroboam ordained a feast in the eighth month, on the fifteenth day of the month, like unto the feast that is in Judah,.... The feast of tabernacles, which was on the fifteenth day of the seventh month; this was done chiefly for the sake of an alteration; though Abarbinel thinks, because the fruits of the land were not so soon ripe nor so soon...
1Ki 12:30-31 But this institution became a sin to Jeroboam, because it violated the fundamental law of the Old Testament religion, since this not only prohibited all worship of Jehovah under images and symbols (Exo 20:4), but had not even left the choice of the place of worship to the people themselves (Deu 12:5.).
Commenting on 1 Kings 12:30-31