He commanded Judah to seek Yahweh

Here the word "Judah" represents the people of Judah. Worshiping Yahweh is spoken of as if it were seeking him. AT: "He commanded the people of Judah to worship Yahweh" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-metaphor)