Jamieson, Fausset and Brown on Matthew 20:15

15. Is it not lawful for me to do what I will with mine own? Is thine eye evil, because I am good?--that is, "You appeal to justice, and by that your mouth is shut; for the sum you agreed for is paid you. Your case being disposed of, with the terms I make with other laborers you have nothing to do; and to grudge the benevolence shown to others, when by your own admission you have been honorably dealt with, is both unworthy envy of your neighbor, and discontent with the goodness that engaged and rewarded you in his service at all."