'Single, simple, undivided' — the healthy eye of Matthew 6:22 (KJV 'single'; NWT 'simple'; NIV 'healthy'), opposed to the 'evil eye,' which in Hebrew idiom is the STINGY eye (Deuteronomy 15:9). Generosity as optics: the undivided eye lights the whole body — and the very next sentence is about divided service: no one can be a slave to two masters. → first discussed at Matt 6:22