John Wesley on Matthew 6:22

The eye is the lamp of the body - And what the eye is to the body, the intention is to the soul. We may observe with what exact propriety our Lord places purity of intention between worldly desires and worldly cares, either of which directly tend to destroy. If thine eye be single - Singly fixed on God and heaven, thy whole soul will be full of holiness and happiness. If thine eye be evil - Not single, aiming at any thing else.