12 Therefore, let us not only avoid sins, but those things too which seem to be indifferent, yet by degrees lead us into these misdeeds. He, indeed, who walks by the side of a precipice, even though he may not fall over, trembles; and very often he is overset by this same trembling, and falls to the bottom. So also he who does not avoid sins from afar, but walks near them, will live in fear, and will often fall into them. Besides, he who eagerly looks at strange beauties, although he may not commit adultery, has in so doing entertained lust; and has become already an adulterer according to the declaration of Christ; and often by this very lust he is carried on to the actual sin. Let us then withdraw ourselves far from sins. Do you wish to live soberly? Avoid not only adultery, but also the licentious glance! Do you wish to be far removed from foul words? Avoid not only foul words, but also inordinate laughter, and every kind of lust. Do you wish to keep far from committing murders? Avoid railing too. Do you wish to keep aloof from drunkenness? Avoid luxury and sumptuous tables, and pluck up the vice by the roots.
Source: Homilies on the Statues (New Advent)