Rashi: It is tightly attached to idolatry, and cannot separate. Therefore, the Navi ceases to prophesize and rebuke it, for it will not help.

Radak: Atzabim are the calves, Ba'al and Asherah. Efrayim is so attached to them that there is no solution; it will not heed words of rebuke.

Malbim: Their king is connected to idols, and does not want to separate from their company, like it says about Yaravam ben Yo'ash "va'Ya'as ha'Ra b'Einei Hashem Lo Sar mi'Kol Chata'os Yaravam ben Nevat" (Melachim II, 14:24).

Radak: This is said to the Navi. Cease to rebuke it, for it will not help. This is a metaphor for one who is angry at his friend; he will not hear his rebuke. He says, since you do not hear me, I will never rebuke you. Even so, after a while he returns to rebuke him.

Malbim: I command you, Yehudah, to separate from him ¹ ; do not come to Gilgal and mix with him.