27 You have heard that it was said to them of old: Thou shalt not commit adultery. 28 But I say to you, that whosoever shall look on a woman to lust after her, hath already committed adultery with her in his heart.
Augustine: Forasmuch as all such acts of lust pollute and destroy God’s image (which you are) [1 Cor 3:16], the Lord who knows what is good for you, gives you this precept that you may not pull down His temple which you have begun to be.
Jerome: Passion is at once a sin; the spontaneous movement of the mind, though it partakes of the evil of sin, is yet not held for an offence committed.
Gregory: Whoso casts his eyes about without caution will often be taken with the pleasure of sin, and ensnared by desires begins to wish for what he would not. Great is the strength of the flesh to draw us downwards, and the charm of beauty once admitted to the heart through the eye, is hardly banished by endeavour. We must therefore take heed at the first, we ought not to look upon what it is unlawful to desire. For that the heart may be kept pure in thought, the eyes, as being on the watch to hurry us to sin, should be averted from wanton looks.
Chrysostom: If you permit yourself to gaze often on fair countenances you will assuredly be taken, even though you may be able to command your mind twice or thrice. For you are not exalted above nature and the strength of humanity. She too who dresses and adorns herself for the purpose of attracting men’s eyes to her, though her endeavor should fail, yet shall she be punished hereafter. . . . What the Lord seems to speak only to the man, is of equal application to the woman.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. I (London: Rivington, 1842).