en_tn/2ch/20/03.md

set himself to seek

This is an idiom. AT: "determined himself to seek" or "devoted himself to seek" (See: rc://en/ta/man/translate/figs-idiom)

to seek Yahweh

This speaks of seeking Yahweh's advice as if he were looking for Yahweh. AT: "to seek Yahweh's advice" (See: rc://en/ta/man/translate/figs-metonymy)

He proclaimed a fast

The word "fast" can be expressed as a verb. AT: "He proclaimed that all the people should fast" (See: rc://en/ta/man/translate/figs-abstractnouns)