en_tn/isa/62/08.md

by his right hand and by the arm of his strength

The right hand and arm represent power and authority. AT: "by his power and authority" (See: rc://en/ta/man/translate/figs-metonymy)

Surely I will no longer give your grain as food for your enemies

This means Yahweh will not let enemies conquer the people of Israel and take their grain anymore. Perhaps enemies took the grain in the past as a tax or to feed their own armies.

I will no longer give your grain as food for your enemies ... Foreigners will not drink your new wine

These statements are set together for emphasis and completion. (See: rc://en/ta/man/translate/figs-parallelism)