Bible Dictionary
SINGLE, EYE
Jesus’ teaching about the single eye contrasts spiritual clarity with inward darkness. A sound or undivided outlook is associated with light, while an evil or covetous outlook leaves a person spiritually dark.
Biblical Usage
Jesus connects the condition of the eye with the condition of the whole person: a single eye brings light, while an evil eye brings darkness. The expression may also carry the contrast between generosity and covetousness in the context of love of money.