If the eye is once inflamed

(Thomas Watson, "The Lord's Prayer")

If we would be kept from actual sins--let us be careful to avoid all the inlets and occasions of sin.

Do not run into evil company. He who would not catch the plague--must not go into an infected house.

Guard your senses, which may be the inlets to sin. Keep the two portals--the eye and the ear. Especially guard your eyes. Much sin comes in by the eye; the eye is often an inlet to sin; sin takes fire at the eye.

The first sin in the world, began at the eye. "When the woman saw that the fruit of the tree was good for food and pleasing to the eye--she took some and ate it." Genesis 3:6

Intemperance begins at the eye,
"Do not gaze at wine when it is red, when it sparkles in the cup. In the end it bites like a snake and poisons like a viper!" Proverbs 23:31-32

Covetousness begins at the eye. "When I saw among the spoils a goodly Babylonish garment, and a wedge of gold, I coveted them and took them." Joshua 7:21

The fire of lust begins to kindle at the eye. David walking upon the roof of his house, saw a woman washing herself, and she was, says the text, "beautiful to look upon," and he sent messengers and took her, and defiled himself with her. 2 Samuel 11:2.
Looking begat lusting!

Therefore watch your eyes! Job made a covenant with his eyes. Job 31:1. If the eye is once inflamed, it will be hard to stand out long against sin. If the outworks are captured by the enemy, there is great danger of the whole castle being captured!