en_tn_condensed/isa/30/15.md

Holy One of Israel

See how you translated this name in Isaiah 1:4.

In returning and resting you will be saved

Repenting is spoken of as if it were physically returning to Yahweh. This can be stated in active form. Alternate translation: "I will save you from your enemies if you will repent and rest knowing that I will take care of you" (See: rc://en/ta/man/jit/figs-metaphor and rc://en/ta/man/jit/figs-activepassive)

resting

It is implied that the people rest because they trust that Yahweh will take care of them. (See: rc://en/ta/man/jit/figs-explicit)

in quietness and in trust will be your strength

Quietness here refers to not being anxious and worried. It is implied that they are not worried because they trust in Yahweh. Alternate translation: "You will be strong if you are quiet and trust in me" (See: rc://en/ta/man/jit/figs-explicit)