en_tn_condensed/ecc/05/13.md

under the sun

This refers to things that are done on earth. See how you translated this in Ecclesiastes 1:3. AT: "on the earth" (See: rc://en/ta/man/translate/figs-idiom)

riches hoarded by the owner

This can be stated in active form. AT: "an owner hoards riches" (See: rc://en/ta/man/translate/figs-activepassive)

through bad luck

Possible meanings are 1) "through misfortune" or 2) "through a bad business deal."

his own son, one whom he has fathered, is left with nothing in his hands

Here the phrase "in his hands" represents ownership. This can be stated in active form. AT: "he leaves no possession for his own son" (See:rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-activepassive)