The supply is called a staff because some people need a staff to walk and do their work, and people need bread to live. Bread represents all kinds of food. AT: "the supply of food" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-synecdoche]])
You may need to make explicit why they will ration the bread. "they will carefully divide their bread because they fear that there will not be enough" (See: [[rc://en/ta/man/translate/figs-explicit]])
The word "shaking" is a metaphor for being afraid and "trembling" represents fear. AT: "rationing it while shaking" or "rationing it in fear" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Possible meanings are 1) "everyone will look at his brother and worry about how much food his brother eats and waste away" or 2) "every one of them will be dismayed and waste away" (See: [[rc://en/ta/man/translate/figs-explicit]])
The phrase "waste away" is usually used of flesh or wood rotting. Here it is a metaphor for wicked people becoming thin and dying because they have no food. (See: [[rc://en/ta/man/translate/figs-metaphor]])