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