Catena Aurea on Matthew 5:29–30: Augustine of Hippo

As the eye denotes contemplation, so the hand aptly denotes action. By the eye we must understand our most cherished friend, as they are wont to say who would express ardent affection, ‘I love him as my own eye.’ And a friend too who gives counsel, as the eye shews us our way. The “right eye,” perhaps, only means to express a higher degree of affection, for it is the one which men most fear to lose.

Or, by the right eye may be understood one who counsels us in heavenly matters, and by the left one who counsels in earthly matters. And this will be the sense; Whatever that is which you love as you would your own right eye, if it “offend you,” that is, if it be an hindrance to your true happiness, “cut it off and cast it from you.” For if the right eye was not to be spared, it was superfluous to speak of the left. The right hand also is to be taken of a beloved assistant in divine actions, the left hand in earthly actions.