Rashi: He tells them the words of His quarrel with their brothers Beis Yisrael.

Radak: Even though Yehudah "Od Rad Im Kel" (1), and persisted in Avodas Kel in the Beis ha'Mikdash, afterwards they did evil, when their kings were evil. Therefore, Hashem has a quarrel and rebuke with them.

Malbim: This means that Efrayim quarrels with Yehudah - this is a feud against Hashem. In those days there was hostility between Efrayim and Yehudah. Yehudah served Hashem and guarded Avodas ha'Mikdash and its Korbanos, and Efrayim clung to Chatas Yaravam and quarreled with Hashem. This feud was with Yehudah and caused Efrayim's fall. Not only did Yehudah not help Efrayim in Efrayim's affliction - in the days of Achaz, [Yehudah] incited Melech Ashur against Efrayim (Melachim II, 16:7).

Malbim (4): Efrayim feuded with Yehudah, to resemble Yakov, who feuded with his brother.

Rashi: [Hashem will tell Yehudah,] lest they be astounded when He punishes Yakov (the 10 tribes) like their ways.

Radak: Their kings were evil. They did not remember My Chesed with them, and not with their father Yakov. Everything was for his seed! I showed to him a sign she'Yihyeh (that will be ¹ ) to his seed if they will put their hearts to Me. They will know that the sign was for them, and not for Yakov himself. He was not a master to Esav in his lifetime! His seed does not recognize that the sign was for them. If they did, they would cling to Me and My Avodah, and I would fulfill for them the Brachah of Yakov their father.

Malbim: The 10 tribes attribute to themselves the name Yakov. Stam 'Beis Yakov' refers to the 10 tribes. Whenever Yisrael and Yehudah are mentioned together, Yisrael refers to the 10 tribes. The verse mentions a feud with Yehudah, and rebelling against Hashem and serving the calves - this is a metaphor that they want "Lifkod Al Yakov ki'Drachav", i.e. to resemble Yakov. They quarrel with their brother Yehudah, for also Yakov Avinu fought with his brother.