וַיְהִ֛י הַדָּבָ֥ר הַזֶּ֖ה לְחַטָּ֑את וַיֵּלְכ֥וּ הָעָ֛ם לִפְנֵ֥י הָאֶחָ֖ד עַד־דָּֽן׃
And this thing became a sin; for the people went to worship before the one, even unto Dan.
From David to Destruction
As Melachim I 12:30 notes, “VeYehi HaDavar HaZeh LeChatat,” “and this matter became a sin.” In other words, Yarav’am’s reforms lead to spiritual catastrophe. According to the Metzudat David (ad. loc.),49The matter is subject to an intense debate among the Rishonim. Yarav'am first directs the aberrant service to Hashem; however, the service eventually (presumably during the time of Achav) devolves into outright Avodah Zarah. As noted in Melachim I 19, during Achav’s reign, barely seven thousand of the northern Bnei Yisrael are not devoted to Avodah Zarah.