Here "Ephraim" represents the whole northern kingdom of Israel, which is a metonym for the people who live there. They chose to worship idols, instead of Yahweh. Yahweh is commanding Hosea to not try to correct them. The people of Israel will not listen. (See: [[rc://en/ta/man/translate/figs-synecdoche]] and [[rc://en/ta/man/translate/figs-metonymy]])