Matthew 6:22
"The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light."
Cross References (ranked by relevance)
2 Corinthians 11:3
28
But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ.
Colossians 3:22
Servants, obey in all things your masters according to the flesh; not with eyeservice, as menpleasers; but in singleness of heart, fearing God: