Chapter 9, Verses 18, 19 and 20 - Sun Tzu

When the enemy is close at hand and remains quiet, he is relying on the natural strength of his position. When he keeps aloof and tries to provoke a battle, he is anxious for the other side to advance. If his place of encampment is easy of access, he is tendering a bait.
~ from The Art of War, Giles translation ~

Go here to read the introductory post to the verses of The Art of War.