Luke 11:34

For He gives the name of the eye especially to our understanding, but the whole soul, although not corporeal, He metaphorically calls the body. For the whole soul is enlightened by the understanding. For the understanding from its very beginning desires only singleness, containing no dissimulation, or guile, or division in itself.

(Epist. 41.) Or else; The light and eye of the Church is the Bishop. It is necessary then that as the body is rightly directed as long as the eye keeps itself pure, but goes wrong when it becomes corrupt, so also with respect to the Prelate, according to what his state may be, must the Church in like manner suffer shipwreck, or be saved.

(28. Mor. c. 12.) Or else; By the name body each particular action is understood which follows its own intention, as it were the eye of the spectators. Therefore it is said, The light of the body is the eye, because by the ray of a good intention the deserving parts of an action receive light. If then thy eye be single, thy whole body will be full of light, for if we intend rightly in singleness of heart, we accomplish a good work, even though it seem not to be good. And if thy eye be evil, thy whole body will be full of darkness, because when with a crooked intention even a right thing is done, although it appears to glitter in men's sight, yet before the bar of the internal judge it is covered with darkness. Hence too it is rightly added, Take heed therefore that the light which is in thee be not darkness. For if what we think we do well we cloud by a bad intention, how many are the evils themselves which even when we do them we know to be evil?

But as if the eye of the body be light the body will be light, but if dark the body will be dark also, so is it with the understanding in relation to the soul. Hence it follows, If thine eye be single, thy whole body will be full of light; but if evil, thy whole body will be full of darkness.

(de Cons. Ev. lib. ii. c. 39.) Luke indeed relates this in the same place as Matthew, but in a somewhat different order. But who does not see that it is an idle question, in what order our Lord said those things, seeing that we ought to learn by the most precious authority of the Evangelist, that there is no falsehood. But not every man will repeat another's words in the same order in which they proceeded from his mouth, seeing that the order itself makes no difference with respect to the fact, whether it be so or not.