St Matthew 6:22-24

The light of thy body is thy eye. If thy eye be single, thy whole body shall be lightsome. But if thy eye be evil thy whole body shall be darksome. If then the light that is in thee, be darkness: the darkness itself how great shall it be! No man can serve two masters. For either he will hate the one, and love the other: or he will sustain the one, and despise the other. You cannot serve God and mammon.