Thy wickedness may hurt a man as thou art; and thy righteousness may profit the son (rather, a son) of man. Job must not think, Elihu means, that, because his good actions benefit and his bad actions injure his fellow men, therefore they must also in the one case injure and in the other benefit God.
The cases are not parallel. God is too remote, too powerful, too great, to be touched by his actions. Job has done wrong, therefore, to expect that God would necessarily reward his righteousness by prosper us, happy life, and worse to complain because his expectations have been disappointed.
It is of his mere spontaneous goodness and bounty that God rewards the godly.