The eye is the lamp of the body. So, if your eye is healthy [ἁπλοῦς], your whole body will be full of light, but if your eye is bad [πονηρός], your whole body will be full of darkness. If then the light in you is darkness, how great is the darkness!
—Jesus, Matthew 6:22-23, English Standard Version
The adjective ἁπλοῦς (single, simple, without folds, uncomplicated) is opposed not merely to διπλοῦς (double) but also, here, to πονηρός (evil, wicked, toilsome).