RobH_en_tn/isa/52/10.md

bared his holy arm

Here "arm" represents Yahweh's power. Yahweh showing all the people of the nations that he is holy and powerful is spoken of as if Yahweh were a warrior who removed his cloak, baring his arms for battle. Alternate translation: "showed his holiness and mighty power" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-metaphor)

all the nations; all the earth

Here "nations" and "earth" represent the people of all the nations all over the earth. (See: rc://en/ta/man/translate/figs-metonymy)