Nedarim, Chapter Three, Mishnah Seven
This mishnah deals with a person who swears that he will not receive benefit from a type of people whom he calls those who see the sun.
He who vows [not to benefit] from those who see the sun, is forbidden [to benefit] even from the blind, because he meant those whom the sun sees.
Those who see the sun does not only mean those who can see but can also mean those who live under the sun, i.e. everybody. Hence he may not benefit from anybody.