RobH_en_tn/psa/062/010.md

oppression or robbery

These two words have basically the same meaning. You cannot trust in money that you get by taking it from other people. (See: rc://en/ta/man/translate/figs-doublet)

for they will bear no fruit

The writer speaks of riches as if they were trees or vines that could bear fruit. Alternate translation: "for they will provide nothing good for you" (See: rc://en/ta/man/translate/figs-metaphor)

do not fix your heart on them

Here "fix your heart" is an idiom that means to desire something greatly. Alternate translation: "do not desire them" (See: rc://en/ta/man/translate/figs-idiom)