Luke 11:35 in the King James Version
Take heed therefore that the light which is in thee be not darkness.
Context
34 The lamp of the body is the eye. Therefore when your eye is good, your whole body is also full of light; but when it is evil, your body also is full of darkness.
35 Therefore see whether the light that is in you isn’t darkness.
36 If therefore your whole body is full of light, having no part dark, it will be wholly full of light, as when the lamp with its bright shining gives you light.”